> There are organizations that might sue to enforce the GPL license, even if the original copyright holders might not because they are defunct.

This is exactly what I'd like to dig into further. Who else besides the copyright owner has the legitimacy to enforce the GPL?

Afterall, how can a random external entity know whether or not I have a legitimate non-GPL, commercial, license granted by the copyright holder? There are many dual licensed GPL projects out there.

> Note that someone owns that copyright, because someone owns the IPR of that company, even if it is defunct.

This is very interesting as well. So basically you're saying that as part of the closing of the company, the IPR must be transfer to some other entity/individual.