There is a decent chance that model weights are not copyrightable (and I think that's the clearest definition of the law, I don't think they're a compiled work,

There is a decent chance that model weights are not copyrightable (and I think that's the clearest definition of the law, I don't think they're a compiled work, at most they might be patentable. Particularly in situations where multiple models might converge towards the same weights, that seems more like a discovery than a creative act? That being said, I don't feel like I know for certain how a court would rule. And I wouldn't like to fight Facebook about it in court regardless, that sounds like a pretty bad time even if the court sides with you. But on the other hand, Facebook might not be keen to test this either.