[mannerheim]

> You could charge engineer hours, but who knows how many they would have contributed.

I would guess courts have ways of determining this, perhaps via subject matter experts. It's not like GPL software is the only kind of software for which it might be impossible to obtain a proprietary license - there are probably many cases of proprietary software copying from other proprietary software, where one party isn't willing or able to provide a license to another (for instance, a company might be competing in the same space as another that copied their code, so they're unwilling to provide a license). But more likely a settlement would be reached in a case of clearcut copyright infringement.