> You look for copyright notices, ask the holders whether they own all > of that, ask the distributor who owns any other bits. If they don't > know or won't tell, they're up for contributory infringement,
No, they're not because you have no contractual relationship with them. Back when NYU was distributing public versions of GNAT, if somebody was to ask AdaCore "are the file in there that say they have your copyright really yours", AdaCore would most certainly decline to answer and say "we have no idea what NYU is distributing: yes, they got it from us originally, but we have no idea if they modified it". Why should they say more? What's in it for them? Same thing if you went and asked FSU about the files that have their copyright. For that matter, I doubt the FSF would answer either. If some large defense contractor got a copy of GCC from a subcontractor and wanted to verify with the FSF that this was really GCC, do you think the FSF would take the time to do a comparison to answer the question? I doubt it! And since they have no obligation to do anything, they can't be held liable for not doing it. Indeed it would be unreasonable for them to take the time to inspect the sources in question to verify that everything that's claimed to be there's really is. > When you receive a copy of Microsoft Windows from a reseller on a > street corner, how do you know who else, if anybody, might have a > copyright claim on it? Why do you think that Microsoft goes to so much trouble to protect their CD's with things like holograms? Precisely to help provide an answer to this question. But even with that, if it's somebody on a street corner, you really DON'T know that it isn't counterfeit and might infringe somebody else's copyright. If it's in a reputable store and it looks like undamaged Microsoft packaging, you have much more reason to trust it. > If the redistributor doesn't have any copyright claims on the file, > you can ask for a contract, an agreement, a warranty promise, whatever > you ask for and they agree to give you, but it's not going to be a > copyright license. I'm not sure what a "copyright license" means. A "software license" is a contract that states under what terms you can use copyrighted software. That's exactly what you'd be getting from the redistributor. If it were pure GPL software, the license would just be a copy of the GPL along with a statement that everything in it is subject to the GPL.
