I believe [program] violates GPL, do I need to sue the author before using its source code? Let's say there's a program (&quot;ABC&quot;) which is licensed under GPL. There's a similar program (&quot;CAD&quot;) on the market, which I believe is a modified ABC. It is therefore in violation of the GPL. Am I allowed to take and use (or reverse engineer) CAD's source code without the author's consent, or do I need to sue CAD's author first for violating GPL? Looks related: What are the potential legal consequences for a company that has GPL violations? The answer to that question makes me suspect the answer to this question is &quot;yes&quot;, but I'm not sure, since I can potentially be wrong about CAD.
It's possible that CAD has a separate licence from the authors of ABC that allows them to produce a closed source copy. If not, they have no right to distribute CAD. However two wrongs don't make a right, and so you don't get to violate the copyright of CAD.* Unfortunately, unless you are one of the authors of ABC, you have no standing to sue the authors of CAD. You can only notify the authors of ABC and hope they do. If the authors of ABC don't have the resources to pursue the matter, you may be out of luck. That's one of the reasons the FSF gets copyright assignments for their projects. * It turns out that this is a much more debateable issue than I first thought. Some courts have held that an unauthorized derivative work is not copyrightable.
You probably can. There are a few questions here. First, is the message protected by copyright? In general, it probably is, but there are many exceptions that might allow you to use it without permission. Unfortunately, these exceptions vary from jurisdiction to jurisdiction. The exceptions tend to allow the use of small excerpts of a work for various sorts of purposes that don't undermine the copyright holder's ability to profit. That leads to the second question, which is why you are using that message. If you're including it in your source code so you can test whether a message generated at run time is in fact that message, that's one thing, and it's probably okay. On the other hand, if the owner of the copyright sells a database of all its message strings, and you're compiling a similar database that you also intend to sell, that's probably not okay. A third question concerns the Firefox license terms. It's entirely possible that they allow you explicitly to do what you're considering, in which case it doesn't matter what copyright law says about it. On the other hand, Firefox is open source software, and under some open source licenses, if you incorporate any of the source code in your own product, you are required to release your product's source code under the same license. If you're not already planning to do that, you should consider carefully whether including that error message would trigger that provision (if there is one) of Firefox's open source license.
Without a license, you have no right to copy or distribute someone else's work. Suppose you copy or distribute against the terms of the license. Either you didn't agree to the license, and therefore had no right to do as you did; or you did agree and still violated the terms of the license anyway. By the law of the excluded middle (accepted or not accepted), you infringed either way.
Hypothetically speaking, if a program doesn't come with a EULA, does that mean someone in possession of it (who isn't the owner) would be breaking the law if they used it? If the copy on the stick was lawfully made with permission of the copyright holder, then you can lawfully use the software. Someone who lawfully comes into possession of a lawfully made copy of the software (that was not a backup) has the right to use that software in the ordinary way. For example if someone found a USB stick lying on the ground and it had software on it but no EULA, could they use the software? Maybe, but it would be hard for them to know whether they could or not. It might be a backup. It might be an unlawful copy. There was a case where a person found a CD in the trash that was clearly an original. The package had a shrink wrap agreement, but he found the CD without the package. The court held that he had every right to use the software on the CD (since it was a lawfully-made copy and not a backup) and was not bound by the EULA (since he hadn't opened the package). But he was very fortunate in being able to demonstrate these facts.
Software doesn't infringe any patents. Creating a product that includes the software may infringe the patent, and may infringe that patent because the software is included, but the software itself doesn't. Software on its own doesn't have any effect that could be patented, only as part of some machine. On the other hand, if you want to distribute software that is under the GPL v3.0 license, then a requirement is that you give everyone a patent license for all patents that would be infringed by using the software (as part of some machine), and if you are not the patent holder, then in practice that means you are not allowed to distribute the software. With your grand plan that you write software and then let the end users do the patent infringement, that will backfire in two ways: First, you'd be likely sued for contributory patent infringment, because it is you who enables the patent infringemnt. Second, you can be sued for copyright infringement because you have no license that allows you distribution of the software, depending on the Open Source license used.
What happened is that you created a legal mess. You are obviously on the hook for copyright infringement. The maintainers of the project will scramble to replace your code with newly written code. They will likely ask your company which code they are complaining about - that puts your company into the problematic situation that they shouldn't identify code that isn't theirs, that it will be hard to sue for infringing code when they didn't give the project maintainers a chance to fix it, and that everything they identify will be replaced. Since it is your actions that caused the trouble, anyone suffering damages from your actions can sue you.
Whoever "derived" the illegal derivative work most likely has copyright in his derivations, unless they are not worth copyright protections. Say I take the Harry Potter books and add a few chapters and try to sell it - that's copyright infringement of course, but I have the copyright on these additional chapters. However, I don't have the right to allow you to copy the derived work. And even if you have the right to copy the original work, you don't have the right to copy the derived work because it is a different work. I could extract my changes, and allow you to take them and do with them what you like. You could then create an illegally derived work yourself. I couldn't sue you, but the original copyright holder could. To the comments: One, a work and a derivative of the work are not the same, so even if you have the right to make a copy of a work, that doesn’t give you any right whatsoever to copy a derivative work - they are not the same work. Two, the copyright holder has the exclusive right to control copying and the creation of derivative works. If the copyright holder doesn’t want derivatives to exist, then creating them, copying them etc. is always copyright infringement.
The only issue relevant to your age is the (ir)revocability of the license. GPLv3 purports to be an irrevocable license. To be really irrevocable, the license would need to grant certain rights in exchange for something of value, that is, you need a license that passes muster as a contract. Copyright licenses are typically treated as contracts, but it is not clearly established in law that licenses are contracts or are not contracts. Out of the goodness of your heart, you can grant permission to use your property, but you can also withdraw that permission. If you have a contract granting perpetual permission to use your property in exchange for something of value, then you can't later withdraw that permission. In the case of Jacobsen v. Kratzer, the sides advances opposing theories that the license was a "bare license" vs. was a contract. (The matter was ultimately settled out of court). This article puts together the legal factors surrounding the notion of license as contract, see p. 21 ff, and esp. §IV for arguments that licenses should be contracts, to be fully enforceable. A contract for non-essentials formed with a minor is not enforceable, until you are 18. You could therefore revoke the license, until you are 18. Anyone who uses the software does so at their peril. However, if the license is not a contract, no existing legal doctrine (in the US) whereby the permission is irrevocable. In other words, yes you can, at their peril. The whole license-as-contract issue is very complicated, and I'm only focusing on the revocability issue. There is a separate question whether one can sue a user for both copyright infringement and breach of contract. The case of Artifex v. Hancom, see also this analysis, found that (in the particular case), plaintiff can pursue the matter as both infringement and contract breach.