Unrelated question regarding this part, since you seem to be an expert on this:

> If what you do with a copyrighted work is covered by fair use it doesn't matter what the license says - you can do it anyway.

How is it that contracts can prohibit trial by jury but they can't ban prohibit fair use of copyrighted work? Is there a list of things a contract is and isn't allows to prohibit, and explanations/reasons for them?

> I am excruciatingly aware of the difference between a copyleft license and the public domain.

Then why did you say "no harm was caused"? Clearly the harm of "using our copylefted work to create proprietary software" was caused. Do you just mean economic harm? If so, I think that's where the parent comments confusion originates.

> The GFDL imposes restrictions on distribution, not copying, so merely downloading a copy imposes no obligation on you and so isn't a copyright infringement either.

The restrictions fall not only on verbatim distribution, but derivative works too. I am not aware whether model outputs are settled to be or not to be (hehe) derivative works in a court of law, but that question is at the vey least very much valid.

Models, however, can reproduce copyleft code verbatim, and are being redistributed. Doesn't that count?

Licences like AGPL also don't have redistribution as their only restriction.

That's really interesting. I'm a lawyer, and I had always interpreted the license like a ToS between the developers. That (in my mind) meant that the license could impose arbitrary limitations above the default common law and statutory rules and that once you touched the code you were pregnant with those limitations, but this does make sense. TIL. So, thanks.

But fair use is dependent on you getting the work legally. Is downloading a book with the intention of violating the GFDL a legal way of acquiring it.

This means that you can ignore any part of licenses you don't want to and just copy any software you want, non-free software included.