Putting the GNU back into GNU Radio 4.0#781
Conversation
This relicenses GNU Radio 4.0 from MIT to **LGPL-3.0-or-later** with a **static linking exception** (SPDX: `LGPL-3.0-or-later WITH LGPL-3.0-linking-exception`). **This is a draft PR open for review and comment until Labour Day, or latest by 11 May 2026** before merge. We welcome substantive feedback — see discussion guidelines at the bottom. --- ### History GNU Radio 4.0 was originally licensed under LGPLv3 when development began in December 2022. In mid-2025 we relicensed to MIT — a deliberate, time-bounded experiment. We could do this because GSI/FAIR is the principal author and copyright holder of the GR4 codebase, and held the rights to set the license accordingly. This was targeted at specific commercial actors who had stated intentions to adopt, contribute to, co-maintain and publicly acknowledge GR4 in their products and services. The MIT terms were intended to remove every last licensing friction in their way. The community contributors kept showing up — researchers, OOT block-library authors, GSoC participants, individual hobbyists. The adoption, contribution, and public acknowledgement that the relaxed terms were intended to unlock did not materialise on a scale that justified the trade-off. Without that vested co-interest from the partners the experiment was aimed at, MIT's justification fell away. The costs and legal risks of running under permissive terms remained — no longer balanced by benefit to the wider open-source community or to the people maintaining GR4. Returning to LGPL with a static linking exception preserves every practical permission users currently rely on — proprietary applications, embedded, WASM, static linking — and keeps the door fully open for commercial use, including products and derivatives built on top of GR4. It restores reciprocity between users and the contributors maintaining the project. This is not a move against commercial use; it supports commercial use on terms sustainable for everyone involved. --- ### What changes for users **For users and contributors, the day-to-day experience does not change.** You can still use GNU Radio 4.0 freely in any application — proprietary, commercial, embedded, WASM, statically linked — without disclosing your own source code. The static linking exception explicitly preserves this. What does change is what you do if you **modify the library itself** (the GR4 core source files): those modifications must be shared back under the same terms (weak copyleft). This keeps improvements flowing back to the community and keeps the library safe to build on long-term. --- ### Why #### Reciprocity for the community The LGPL ensures that **everyone benefits from improvements** to the library, regardless of who makes them. If you improve GNU Radio, everyone gets that improvement. #### [Public Money? Public Code!](https://publiccode.eu/) GSI/FAIR is a [signatory](https://publiccode.eu/supporters/) of the [Public Money? Public Code!](https://publiccode.eu/) campaign by the Free Software Foundation Europe. GSI/FAIR is publicly funded by German, EU, and FAIR member-state contributions. The LGPL ensures that improvements to publicly funded infrastructure remain publicly available. Public money funded the work. The code stays public. And modifications to publicly funded code should stay public too. #### [FAIR Principles](https://www.go-fair.org/fair-principles/) The FAIR data principles — **F**indable, **A**ccessible, **I**nteroperable, **R**eusable — guide how publicly funded research outputs should be managed. The LGPL supports these principles by ensuring the library remains reusable by everyone, while requiring that modifications to the shared core are accessible to all. #### The name says it GNU Radio has "GNU" in its name. The LGPL is the natural license for a GNU library: it protects the freedom of the library while allowing it to be used in any application. This has been and will always be the spirit of the project. #### Patent peace for everyone LGPL carries a clear, written promise from each contributor: they will not later sue users — including commercial users — over patents covering the code they contributed. The static linking exception does not affect this; it changes only the linking rules. In practice this matters because patents have long lives, and companies behind contributions get acquired, merge, or wind up. If a patent later changes hands, the LGPL contribution still carries the written record that downstream users — including anyone building commercial products on GR4 — already have permission to use the technique. That record protects those products from surprise patent claims years after the fact. This is not a restriction on commercial use; it is a benefit that flows to commercial users. The patent grant reaches every recipient — hobbyist, researcher, integrator, downstream vendor — and stays attached to the patent through acquisitions, mergers, or bankruptcies. Build what you want on top of GR4. The patent question stays settled. --- ### What the static linking exception means The standard LGPL requires that users of statically linked applications provide object files or relinking capability. This is impractical on embedded platforms, WASM, and in some industrial and institutional contexts. The static linking exception (a standard [SPDX-registered exception](https://spdx.org/licenses/LGPL-3.0-linking-exception.html) used by many projects) waives this specific requirement. **In plain terms:** - You may build proprietary applications that link to this library. Your application code is yours. - Only modifications to the library source must be shared. - This applies equally to static linking, dynamic linking, and WASM compilation. See `LINKING_EXCEPTION.md` for the full text and a plain-language summary. Compared to the plain LGPL used by glibc, Qt, and GTK, the static linking exception removes the relinking obligation that makes plain LGPL impractical for static and WASM builds. Compared to MIT, the new requirement is narrow: changes to the library source must be shared back; everything else is unchanged. --- ### What this means for existing MIT releases All code previously released under MIT **remains MIT**. We are not revoking any previously granted rights. Previous MIT releases and their git history remain available under MIT terms indefinitely. --- ### What this means for contributors By submitting contributions to this repository, you agree that your contribution is licensed under the same terms (LGPL-3.0-or-later WITH LGPL-3.0-linking-exception). Past contributions made under MIT remain available under MIT in the historical record; going forward, all new contributions are under LGPL-3.0-or-later WITH LGPL-3.0-linking-exception. --- ### Summary | Aspect | Before | After | |---|---|---| | License | MIT | LGPL-3.0-or-later | | Static linking exception | n/a | Yes ([SPDX registered](https://spdx.org/licenses/LGPL-3.0-linking-exception.html)) | | Use in proprietary apps | Yes | Yes (unchanged) | | Static/embedded/WASM use | Yes | Yes (unchanged) | | Modify GR4 source and keep private | Yes | No — share modifications | | Previous MIT code | — | Remains MIT (git history) | | SPDX identifier | MIT | LGPL-3.0-or-later WITH LGPL-3.0-linking-exception | --- ### What else changes in this PR Beyond the license, this PR also adds documentation that reflects how the project actually operates: - **SUPPORT.md** — support expectations, out-of-tree development model, and how to get the most out of limited maintainer time - **GOVERNANCE.md** — decision-making, roles, and prioritisation - **CONTRIBUTING.md** — updated license terms, PR etiquette, LLM policy, scope and priorities - **LINKING_EXCEPTION.md** — plain-language explanation of the static linking exception - **Issue templates** — structured bug reports, feature requests, and question routing to Discussions --- ### A note on where we stand GNU Radio 4.0 exists because people cared enough to build it. GSI/FAIR has developed this framework as an international public research institution, investing public resources because we believe in open-source collaboration and because the technology serves our scientific mission and the broader community. GNU Radio's history — from Eric Blossom's pioneering work through Tom Rondeau's stewardship, Derek Kozel's and Josh Morman's leadership and the many contributors who made GNU Radio what it is — has deeply informed the development of GR4. We are committed to carrying that pioneering spirit forward. The LGPL reflects that commitment. Free software should remain free. Use it freely, build what you want with it, but if you improve the library, share that improvement back. That's all. --- ### Discussion guidelines This draft PR is open for substantive feedback until approximately 11 May 2026. We welcome: - Questions about the license terms and static linking exception - Compatibility concerns for your specific use case - Practical impact on downstream projects - Suggestions for improving the plain-language documentation We ask that discussion stay factual and constructive. This PR is about the license text and its practical implications. Broader project history is, of course, also welcome on Matrix.
|
|
I have reviewed this PR along with others in the GNU Radio leadership, and we have significant concerns about moving forward with this in its current form. We want to start by acknowledging the extraordinary work that GSI/FAIR has put into GNU Radio 4. The architecture, implementation, CI, review burden, and day-to-day maintenance have required a very large sustained effort. GNU Radio 4 would not be where it is without that work, and the GNU Radio project recognizes and appreciates that contribution. We also understand the motivation behind wanting reciprocity for future improvements to the core library, especially from the perspective of a publicly funded research institution. That is a legitimate topic for discussion. However, we do not think this proposal should move forward in its current form as the basis for the canonical GNU Radio 4 release line. Our concern is not limited to the legal mechanics of GNU Radio 4 has been developed and promoted as the next-generation core of the GNU Radio ecosystem. Even though the main development repository has lived under GSI/FAIR infrastructure, the name, community expectations, conference messaging, and adoption path have all been tied to GNU Radio as a community-governed project. GNU Radio has also made an intentional transition away from BDFL-style project control toward community-sourced, consensus-based governance. That transition matters here. For a project carrying the GNU Radio name, major decisions about licensing, release stability, roadmap authority, and repository stewardship need to be made through GNU Radio governance, not simply communicated to it based on a single institution’s needs. The current PR text describes the MIT licensing period as a time-bounded experiment aimed at reducing adoption friction for specific commercial actors. From the GNU Radio project perspective, the move to a permissive GR4 core was not simply a short-term experiment. It was part of a broader adoption strategy: reduce legal friction, support public/private/academic/government collaboration, and create a path for broader investment once users could depend on GR4. That strategy is especially important now. The community is expecting stabilization around the RC series, not a late change in licensing and governance direction before the initial stable release. Even if the static-linking exception addresses many practical legal concerns, many users and institutions will still experience this as instability in the project’s commitments. That matters for adoption, packaging, downstream planning, and potential institutional support. We also want to be clear that this concern is not about minimizing GSI/FAIR’s contribution or copyright position. GSI/FAIR has done the overwhelming majority of the core work. But contribution volume and copyright ownership are not the same thing as community governance. GNU Radio has intentionally moved away from single-person or single-entity project control toward community-sourced, consensus-based stewardship. For something carrying the GNU Radio name, we need the governance model to reflect that. We also recognize that the current arrangement has placed too much implicit burden on GSI/FAIR. GNU Radio needs to make its commitments more concrete. Areas such as packaging, digital communications functionality, Python bindings, user-facing tooling, documentation, block expansion, GSoC mentorship, and release management are things that need to be built by a community of contributors based on their trust in the project. We agree that this has to become more structured. Our alternative proposal is:
We want GSI/FAIR to remain a central technical partner in GNU Radio 4. We want Ralph and the GSI/FAIR team to continue to have a major technical leadership role. But for GNU Radio 4 to succeed as GNU Radio, the project needs governance and stability that adopters can trust beyond any single institution. |
|
Since I have strongly supported the MIT license in the licensing survey done on the GNU Radio community, and I have publicly continued supporting the MIT license thereafter, I will share some thoughts on this PR. They may or may not qualify under the Discussion guidelines listed in the PR description. First of all, choosing a license is a non-technical matter, and it is a decision that belongs to the GNU Radio governance, constituted by the board and general assembly, as you, @RalphSteinhagen, had clear back in 2024. PRs are for technical (code) contributions, so they are not the right platform to propose licensing changes (you also mentioned this in the same comment). I believe that some of the points that are presented in the PR description are not well motivated:
I might have missed something, but I have never seen the license change being identified publicly in this way, either as an experiment (who would be the subjects of this experiment?) or as something temporary. In particular, in the PR in which the license change was merged, I cannot find any mention to an experimental or time-bounded nature for this change.
This is not completely true. At the moment when the license change to MIT was done, the contributors list included a number of people that are not affiliated with GSI/FAIR. My understanding is that none of these people have transferred the copyright of their contributions to GSI/FAIR, so they remain the sole owners of the copyright of these contributions. I reckon that the vast majority of the GR4 codebase has been written by people affiliated with GSI/FAIR. I acknowledge their efforts and technical prowess and thank them for that. But implying that GSI/FAIR can relicense because they are the copyright holders of all the GR4 codebase is inaccurate and misleading, both back when the change to MIT was done (presumably with the agreement of all the copyright holders), and now that the change to LGPL-3.0-or-later WITH LGPL-3.0-linking-exception is proposed.
At the moment GNU Radio 4.0 does not even have its first stable release. Most potential industry users and contributors of GNU Radio 4.0 would have an understandably conservative approach and wait for the software to be more stable before making a major commitment or investment. The sentence seems to hint at a large influx of GNU Radio 4.0 users and contributors from non-technical areas, but that is not true. The low adoption of GNU Radio 4.0 has been and continues to be a known problem. There have been specific efforts to try to increment this adoption. The reality is that currently GNU Radio 4.0 has very few users, both in industry and elsewhere. Therefore it is just too soon to draw any conclusions about whether any license is having a positive, negative or neutral effect on the health of the project. Since we do not have the number of GNU Radio 4.0 users to do any proper statistics, I will present some anecdotal evidence. Recently a developer expressed publicly their interest in GNU Radio 4.0 for the specific sake of the new (MIT) license (I figured I would better blur the name of this developer in case they prefer privacy, but I guess anyone interested can find it in the history of the GR4 Matrix channel). Perhaps we should ask this developer if LGPL-3.0-or-later WITH LGPL-3.0-linking-exception would be equally compelling for them and their team. 
On the other hand, I have never seen anyone expressing that they will not use or contribute to GNU Radio 4.0 if it uses the MIT license. I could have missed this, as I don't have eyes everywhere all the time.
What are these costs and legal risks? Without any justification this sentence appears to be sowing FUD. The MIT license is used very broadly. I have never heard of a project having legal issues because they use the MIT license. |
|
@RalphSteinhagen As a contributor with merged commits in the MIT-era codebase, I do not consent to the relicensing of my contributions from MIT to I contributed under DCO sign-off only. The DCO is not a copyright assignment and does not grant a right to relicense. My MIT grant stands; no further license is granted. |
|
Heads-up: extending the comment window through 1 June to give us time to engage carefully with the feedback so far. Comments remain welcome. Thanks all — replies coming over the next few days. |
A Case for Patience: Timing the GNU Radio Relicensing for Maximum ImpactThe opinions expressed here are my own and are not affiliated with or representative of any company or organization. Until recently, a large portion of industry wasn't even aware that GNU Radio 4 existed, and for many, that awareness only came to me and others at GRCon 25. When RC1 came out, I was stoked to see a signal processing framework that I could experiment with at work. Before RC1 though, it was a hard sell to my boss on making a bet on something that hadn't even solidified yet. As a software engineer with over five years of experience working in the software and RF industry, I can say that milestones such as a first Release Candidate matter more than it might seem from inside the community to adopt in industry. With that in mind, here is an idea that I would like to present: Hold off on the re-licensing until GRCon 26.In the meantime, GNURadio should publish a clear, visible post on gnuradio.org about the second RC. The reality is that most people in industry saw "GPL" on GNU Radio 3 and could not touch it with a ten foot pole. Once they see that, most don't go digging even further. Luckily, I am not like most :) It's also important to recognize that everything done within a company carries risk. When I first saw that the licensing was changing, and in a PR, I might add... It made me fall out of my chair, since I thought it would not be valid to use at work. Luckily for me, that was not the case. Although, Elasticsearch re-licensing was a well-known example of how a sudden shift can erode trust and force difficult internal conversations about whether a dependency is safe to keep, or even make a bet on. This actually happened to me at the beginning of my career. Providing a clearly communicated time window, for example, six months after the 4.0.0 stable release, would go a long way toward reducing that perceived risk. Teams would have time to evaluate the change, get legal sign-off if needed, and plan accordingly, rather than feeling blindsided. It's also worth pushing back on the assumption that industry isn't interested in giving back. That's not always the case. The team I work on is actively discussing how to contribute to GNU Radio 4 development outside of our organization, because we care about the project and what they are achieving. I even showed up at the last meetup, and plan to continue showing up, to see what I can learn about the framework, and help it become the PyTorch of the signal processing ecosystem. Announcing the discussion of a re-license at GRCon 26, paired with a stable 4.0.0 release that teams can actually evaluate and build against, creates a compelling story: a modern, capable framework with a licensing posture that finally matches how industry actually works. That combination, especially when communicated transparently and with a reasonable adoption window, is far more likely to capture serious attention than an abrupt announcement tied to an uncertain licensing future. Also, many industry partners that are keeping an eye on GNU Radio, will likely be at GRCON 26. Maybe a poll can be done then. The licensing direction is the right conversation to be having. The question is making sure the ecosystem is ready to receive it, and that the transition is handled in a way that builds confidence rather than eroding it. @daniestevez here is my response to the licensing question you had above. It does impact myself, not due to the license, but the fact that the license was considered being changed right before the first stable release. It sends a signal similar to the one Elasticsearch sent, such that they can change their licensing in a day, and your team gets screwed. That is the only thing that I recommend @RalphSteinhagen be more gentle with, especially for early adopters at this stage. I want to also say thank you to everyone in this discussion. It is clear that you all have passion for this project, and they just want to ensure that the project gets into as many hands as possible. All love in this community! |
5 participants
This relicenses GNU Radio 4.0 from MIT to LGPL-3.0-or-later with a static linking exception
(SPDX:
LGPL-3.0-or-later WITH LGPL-3.0-linking-exception).This is a draft PR open for review and comment until Labour Day, or latest by 11 May 2026 before merge. We welcome substantive feedback — see discussion guidelines at the bottom.
History
GNU Radio 4.0 was originally licensed under LGPLv3 when development began in December 2022.
In mid-2025 we relicensed to MIT — a deliberate, time-bounded experiment. We could do this because GSI/FAIR is the principal author and copyright holder of the GR4 codebase, and held the rights to set the license accordingly.
This was targeted at specific commercial actors who had stated intentions to adopt, contribute to, co-maintain and publicly acknowledge GR4 in their products and services. The MIT terms were intended to remove every last licensing friction in their way.
The community contributors kept showing up — researchers, OOT block-library authors, GSoC participants, individual hobbyists. The adoption, contribution, and public acknowledgement that the relaxed terms were intended to unlock did not materialise on a scale that justified the trade-off.
Without that vested co-interest from the partners the experiment was aimed at, MIT's justification fell away. The costs and legal risks of running under permissive terms remained — no longer balanced by benefit to the wider open-source community or to the people maintaining GR4.
Returning to LGPL with a static linking exception preserves every practical permission users currently rely on — proprietary applications, embedded, WASM, static linking — and keeps the door fully open for commercial use, including products and derivatives built on top of GR4. It restores reciprocity between users and the contributors maintaining the project. This is not a move against commercial use; it supports commercial use on terms sustainable for everyone involved.
What changes for users
For users and contributors, the day-to-day experience does not change.
You can still use GNU Radio 4.0 freely in any application — proprietary, commercial, embedded, WASM, statically linked — without disclosing your own source code. The static linking exception explicitly preserves this.
What does change is what you do if you modify the library itself (the GR4 core source files): those modifications must be shared back under the same terms (weak copyleft). This keeps improvements flowing back to the community and keeps the library safe to build on long-term.
Why
Reciprocity for the community
The LGPL ensures that everyone benefits from improvements to the library, regardless of who makes them. If you improve GNU Radio, everyone gets that improvement.
Public Money? Public Code!
GSI/FAIR is a signatory of the Public Money? Public Code! campaign by the Free Software Foundation Europe (what this means).
GSI/FAIR is publicly funded by German, EU, and FAIR member-state contributions. The LGPL ensures that improvements to publicly funded infrastructure remain publicly available. Public money funded the work. The code stays public. And modifications to publicly funded code should stay public too.
FAIR Principles
The FAIR data principles — Findable, Accessible, Interoperable, Reusable — guide how publicly funded research outputs should be managed. The LGPL supports these principles by ensuring the library remains reusable by everyone, while requiring that modifications to the shared core are accessible to all.
The name says it
GNU Radio has "GNU" in its name. The LGPL is the natural license for a GNU library: it protects the freedom of the library while allowing it to be used in any application. This has been and will always be the spirit of the project.
Patent peace for everyone
LGPL carries a clear, written promise from each contributor: they will not later sue users — including commercial users — over patents covering the code they contributed. The static linking exception does not affect this; it changes only the linking rules.
In practice, this matters because patents have long lives, and companies behind contributions get acquired, merge, or wind up. If a patent later changes hands, the LGPL contribution still carries the written record that downstream users — including anyone building commercial products on GR4 — already have permission to use the technique. That record protects those products from surprise patent claims years after the fact.
This is not a restriction on commercial use; it is a benefit that flows to commercial users. The patent grant reaches every recipient — hobbyist, researcher, integrator, downstream vendor — and stays attached to the patent through acquisitions, mergers, or bankruptcies. Build what you want on top of GR4. The patent question stays settled.
What the static linking exception means
The standard LGPL requires that users of statically linked applications provide object files or relinking capability. This is impractical on embedded platforms, WASM, and in some industrial and institutional contexts.
The static linking exception (a standard SPDX-registered exception used by many projects) waives this specific requirement.
In plain terms:
See
LINKING_EXCEPTION.mdfor the full text and a plain-language summary.Compared to the plain LGPL used by glibc, Qt, and GTK, the static linking exception removes the relinking obligation that makes plain LGPL impractical for static and WASM builds. Compared to MIT, the new requirement is narrow: changes to the library source must be shared back; everything else is unchanged.
What this means for existing MIT releases
All code previously released under MIT remains MIT. We are not revoking any previously granted rights. Previous MIT releases and their git history remain available under MIT terms indefinitely.
What this means for contributors
By submitting contributions to this repository, you agree that your contribution is licensed under the same terms (LGPL-3.0-or-later WITH LGPL-3.0-linking-exception).
Past contributions made under MIT remain available under MIT in the historical record; going forward, all new contributions are under LGPL-3.0-or-later WITH LGPL-3.0-linking-exception.
Summary
What else changes in this PR
Beyond the license, this PR also adds documentation that reflects how the project actually operates:
A note on where we stand
GNU Radio 4.0 exists because people cared enough to build it. GSI/FAIR has developed this framework as an international public research institution, investing public resources because we believe in open-source collaboration and because the technology serves our scientific mission and the broader community.
GNU Radio's history — from Eric Blossom's pioneering work through Tom Rondeau's stewardship, Derek Kozel's and Josh Morman's leadership and the many contributors who made GNU Radio what it is — has deeply informed the development of GR4. We are committed to carrying that pioneering spirit forward.
The LGPL reflects that commitment. Free software should remain free. Use it freely, build what you want with it, but if you improve the library, share that improvement back. That's all.
Discussion guidelines
This draft PR is open for substantive feedback until approximately 11 May 2026. We welcome:
We ask that discussion stay factual and constructive. This PR is about the license text and its practical implications. Broader project history is, of course, also welcome on Matrix.