Let's say Person A creates some code and licenses it under a GPL license. If someone (we'll call them Person B) then creates code which derives from Person A's code, but fails to obey the terms of the license and mark their modified code in a GPL compliant fashion, they're at fault and can be held accountable for that.

However, what happens if Person B, prior to being held accountable, tells a new person, Person C, that they can use their code with no restrictions? Person B is at fault for disobeying the license they were presented with, but Person C had no reasonable way of knowing that the code Person B gave them permission to use wasn't actually theirs to give permission for.

What happens to Person C's code in this situation? Are they forced to obey the terms of the license that were not at all communicated to them because of Person B's breach of the license? Or are they somehow exempt from it because they weren't presented with the correct license? What rights does Person A have, and what rights does Person C have?

This is an actual situation I'm dealing with, and I'm not sure how to proceed.

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    Your question describes a situation, which is similar to the mimemagic issue, which happened in 2021. The situation has to be cured, which causes sometimes more, sometimes less chaos. Commented Sep 14, 2023 at 5:28
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    @Martin_in_AUT mimemagic appears to be an interesting case since it essentially forces existing versions of Rails under GPL which in turn puts many projects using Rails under GPL as well, presumably. (That the violating mimeagic versions have been made inaccessible does not fix the Rails versions using them -- it only means you cannot rebuild them from source, but existing binaries are still in violation, iiuc.) What a mess. Commented Sep 14, 2023 at 7:45
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    @Peter-ReinstateMonica Rails did not switch to GPL, they fixed the problem by removing mimemagic from their code base. Old versions (with the license issue) don't seem to be available any more. Commented Sep 14, 2023 at 9:00
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    @Martin_in_AUT Yes, so now Rails is in compliance. But my point is: There are installations of the old, non-compliant versions out there, and potentially sites or other derived work using it which, by association, are non-compliant as well. They believed they were using Rails under the MIT license but they were wrong, much like in this question. Commented Sep 14, 2023 at 10:28
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    @Peter-ReinstateMonica: Just to be clear, Ruby is an interpreter language; there are no compiled binaries involved. Also, GPL compliance isn't required for using GPL code, only for distributing it, so old applications that are still running a retracted Rails version aren't vulnerable to this licensing issue either. (They're probably vulnerable to dozens of unpatched security holes by now, though.) That said, distributing an app that included an old bundled version of Rails would indeed violate the GPL. This isn't how Rails apps are normally distributed, but in principle it could happen. Commented Sep 14, 2023 at 13:06

3 Answers 3


From a software licensing standpoint, C has been in violation of A's licence terms throughout, although hitherto (s)he did not know it. Whilst ignorance of the law excuses nothing, A would have to be pretty hard-hearted to do more than point this out (and to B also). But once C has been clearly informed, (s)he must not continue to distribute this code in violation of the GPL. To do so would be knowingly to violate A's copyright.

Organisations like the Software Freedom Conservancy deal with this sort of situation all the time, and the general community principle is always to bring about compliance, rather than to seek any kind of compensatory remedy. So as long as C brings him/herself into GPL compliance, the matter is very likely to end there. If (s)he doesn't wish to, then as long as (s)he ceases distribution, again, the matter is likely to end there. But there is no legal basis for your idea that C is permanently exempted from A's licence by B's error, and if C continues to distribute in violation, A will be entitled to take action.

There may be grounds for C to make some kind of tortious claim against B; we can't say more because that will depend on jurisdiction and the particulars of the case, and moreover is off-topic for this site.

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    Perhaps worth noting that with the GPL v3, if C brings themselves into compliance within 30 days the matter must end then? Commented Sep 14, 2023 at 8:14
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    I feel that the principle that "ignorance of the law excuses nothing" is not applicable here: C knows the law, but he has been misinformed. If B mislicensed his code with (e.g.) MIT license, one can hardly expect C to - on no grounds - doubt the legitimacy of the license and check for similar work. Of course, A is still the copyright holder and has a right to request B (and C as a consequence) to re-license or remove the work or other measures. Commented Sep 14, 2023 at 13:44
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    "C has been in violation of A's licence terms" is not really accurate. C is in violation of the copyright on A. C didn't accept any valid contract granting a license, and can't violate a contract that doesn't exist.
    – Ben Voigt
    Commented Sep 14, 2023 at 15:09
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    For stolen goods, most jurisdictions rule that if C purchased them in good faith, they have not committed a crime but must still return the goods to A. I agree that it is not ignorance of the law but just ignorance of the facts.
    – jpa
    Commented Sep 14, 2023 at 16:22
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    @jpa: That's for physical goods. The rule for copyright is, you either have a valid license, or you infringe the copyright. For example, US law distinguishes between willful and non-willful infringement, implying that both can give rise to liability. So C infringes A's copyright and is potentially liable. Everything else is a matter of how much grace A is willing to extend to C under the circumstances.
    – Kevin
    Commented Sep 16, 2023 at 1:36

C, who did not know about the license offered by A, could not have agreed to it and is not bound by it. However, without a license from A to do so, C has no right to make and distribute copies of A's copyrighted work, or B's derivative based on A's work. So avoiding the license A offers doesn't help C at all.


What rights does Person A have, and what rights does Person C have?

Person A can sue Person B and Person C for copyright infringement if they can formulate a reasonable damage claim. For instance, if A is offering their software for free under GPL and for $20 under a proprietary license, they could sue B or C for $20 times the number of copies B and C have distributed. If A is not making any money with their software, claiming damages becomes hard/impossible in most countries.

Person C could sue Person B for any damages that A claims from them, plus additional expenses to remove B's code from their software. However, if B has distributed their code under a typical permissive license such as MIT, they would have included a disclamer which frees them from responsibility towards C. Only if C can prove B's malicious intent they could sue them for fraud.

C had no reasonable way of knowing that the code Person B gave them permission to use wasn't actually theirs to give permission for.

This is unlikely to hold in court as a defence. Assuming A have published their GPL software on the Internet, C could have used an open-source scanner to find out the origin of the code they received from B.

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    A can sue C for copyright infringement. C never agrees to A's licensing terms, so it's extremely unlikely that any action for contract violation would succeed. (If you're worried about that, ask an actual lawyer, which I'm not)
    – Ben Voigt
    Commented Sep 14, 2023 at 15:11
  • "if B has distributed their code under a typical permissive license such as MIT" They haven't actually done that, as they had no right to do so. They may have appeared to do so.
    – Ben Voigt
    Commented Sep 14, 2023 at 15:12
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    I don't know much about the conversation here, but do you have to do a search? Is it negligent to not just trust the license you were told? Commented Sep 14, 2023 at 21:33
  • @AzorAhai-him- You don't have to, but it's due diligence in the sense that C is ultimately responsible for the software they distribute. If A can prove that this non-compliant distribution caused them damages, they will be able to get a compensation from C, not from B. Commented Sep 15, 2023 at 11:35
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    @JasonGoemaat: C is not liable for willful infringement, so under 17 USC 504, statutory liability is capped at $30,000 per infringement, but is likely to be significantly lower in practice since C had reason to believe that they had a valid license (and so the court will likely use its discretion to impose a lower statutory damage amount). I agree that $20 is way too low, since the minimum is $750.
    – Kevin
    Commented Sep 16, 2023 at 1:38

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