One question with regard to the GPL: Is it at all enforceable? How could you find out if someone violating it and using your code in a proprietary project?
Well, you have access to the binaries. You could tell if strings are the same pretty easily. I'm sure there's a way to compare more.
No doubt there are people doing it, but the risk is just too large for any sensible company - it would need one malicious person to leak that there was GPL code in a project, and they would have to release the source of the whole project.
Also notable was the long running Cisco case where every time the FSF thought they'd reached an agreement it would be revealed that yet another product violated the GPL.
Note that in the ScummVM case, Atari had no problem with the GPL'd code... until their lawyer informed them that Nintendo's API license didn't allow them to open source code like that. And in Atari's defense the code was outsourced two layers deep to some place in Eastern Europe.
i.e. Atari had no idea there was GPL'd code in there until they were notified. They were cool with keeping to the license until they realized there was a conflict with Nintendo's Wii API license... then they hunkered down and git tight-lipped.
That seems pretty normal. Once the lawyers realized that the company was probably in the wrong, they when into 'damage-control' mode to try and minimize the losses to Atari.
Not necessarily. They would just have to pay a settlement and stop any future distribution of their product that contained GPL'd code.
e.g. They would pay $x to the rights' holder for the code and not distribute the code until the GPL'd version was replaced with a non-GPL'd version. or they would just negotiate a price with the rights' holder for a non-GPL license of the code. (this obviously gets murky when there are multiple rights' holders; especially in code where (major) patch submitters are not required to agree to hand the copyright on their code to the maintainer(s) of the codebase just to get their patch accepted)
