Let's say I see a popular closed source application (distributed for free in binary form) links dynamically with a library that has a GPL license (according to the library's website). Can I write to the company and demand the source code to their app?

  • Yes you can. But only the authors of the library have legal leverage as their rights were violated. Also please finish the question. Commented Apr 23, 2020 at 2:19
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    Contact also gpl-violations.org Commented Apr 23, 2020 at 10:31
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    Also, make sure that said library is not available under other licensees that'd allow such usage (i.e. LGPL/commercial/etc.)
    – Dan M.
    Commented Apr 23, 2020 at 11:52
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    You can demand anything from anyone, but it's quite another thing to get anyone to do anything you've demanded. Commented Apr 23, 2020 at 18:17
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    @BobJarvis-ReinstateMonica very helpful thank you Commented Apr 23, 2020 at 18:53

2 Answers 2


Yes, you can ask for that.

However likely only the authors / the copyright holders of the GPL library will have legal leverage as their copyright has been violated.how exactly will strongly depend on your jurisdiction. Before you go wild, you might want to check that the library copyright holders did not give a special license to the authors of that programme.

Thus I recommend to do both: (a) inform the copyright holders of the library. (b) Ask the authors of the violating programme to give you the sources.

And lobby the library authors to take action, in the same way and to take legal action, if you don't get the sources of the programme - provided that no special license was given to the programme authors. You might also inform the Software Freedom Law Centre, gpl-violations.org and/or FSF. Maybe they can support the library authors in some way in their claim. Legal action is expensive and not necessarily a thing every person wants to burden themselves with for financial or psychological reasons.

However even legal action might not mean that you get the source. Result might just as well be that the programme is withdrawn completely or simply changed to not rely on that library.

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    "Result might just as well be that the programme is withdrawn completely or simply changed to not rely on that library." which wouldn't remove the requirement to provide the source code to people who already had access to the GPL-linked version.
    – wizzwizz4
    Commented Apr 23, 2020 at 14:29
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    @wizzwizz4: Or a settlement or award of damages for infringement that already occurred. Commented Apr 23, 2020 at 22:15
  • @wizzwizz4 there may be no requirement - the original source might be distributed under the GPL, and that might grant further distribution and use with the requirement that your changes and code are also released under the GPL, but that does not automatically mean that you distribute under the GPL. If you don't, then its simple copyright infringement (you have no permission to distribute other peoples code), it does not mean that the GPL is automatically applied. Its an option - follow the GPL or commit copyright infringement.
    – Moo
    Commented Apr 23, 2020 at 23:22
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    @wizzwizz4 basically, if you choose not to distribute under the granted license, you have no license to distribute and therefor are infringing copyright - that does not automatically mean the original license is in force. The copyright holders can sue for infringement and they can offer an outcome whereby damages are reduced or eliminated in exchange for following the GPL, but what they cannot do is force you to follow the GPL. All they can do is stop you from distributing entirely through copyright law.
    – Moo
    Commented Apr 23, 2020 at 23:24
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    This is what the Software Freedom Law Center is for: softwarefreedom.org Commented Apr 24, 2020 at 3:37

It depends. Specifically, it depends on jurisdiction. Yet again, I go back to the "Licences and Contracts" talk at FOSDEM 2018 that I wrote up for LWN. The relevant bit was what are called third-party rights, which specify the extent to which anyone other than the licensor has standing to sue a licensee for failure to observe the terms of the licence.

The opinions of the lawyers giving the talk were that: in England and Wales, no third-party rights exist. In the US, third-party rights likely depend on the precise wording of the licence (which I heard as don't count on it). But in civil law jurisdictions, such as most of Europe, the opinion of the speaker was that third-party rights do exist.

So if you're in such a jurisdiction, it's worth a try. If the company in question is also in such a jurisdiction, it's even more worth trying. Though in the end, planetmaker is right when (s)he notes that litigation is painful and really expensive, so you'll want to do more than just ask for opinions on a community board before you start throwing solicitors' letters around.

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    I would be surprised if civil law jurisdiction was a help there. One of the fundamentals of this system is "no penalty without law". There is no law against not handing out source code when you are obligated to do so. Thus... the only possibility remaining would be to claim that you had damages from not obtaining the sources. Try that and the judges will fall off their chairs, laughing. The only ones who could claim damages are the authors, and they'll have a hard time proving the number that they claim. Worst thing to happen is defendant offers 500 euros, and juge says "well, sounds fair".
    – Damon
    Commented Apr 23, 2020 at 20:36
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    @Damon While I agree that a grant of damages (beyond legal costs) is pretty unlikely (even for the authors), I do believe that, in most civil law jurisdictions, one could sue for specific performance, under the penalty of contempt of court. The article seems to agree with me here.
    – elaforma
    Commented Apr 24, 2020 at 4:08
  • @fNek: Although notably some German courts claimed GPL being an enforcable contract during the 2000/10s, higher courts later turned that down, for example the OLG Hamm. I do not find the court's argument which is basically "given away for free, so where are the alleged damages!" surprising at all. Sure, there's is right and wrong and there's what people should do, but that's not what the law lends for, really. There's no justice in jurisdiction. Unless a law is made, or at least a federal court (and I'm not aware of any such thing) makes a clear statement, I deem this hopeless.
    – Damon
    Commented Apr 24, 2020 at 8:32

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