I believe so. Fair use allows that. If you were to try to hijack the APIs by extending them (in a proprietary way) then you'd possibly be open to litigation.

I'd agree that the court was right to dodge the issue of copyrightability by going for the most narrow interpretation, it's for the lower courts to decide.

Having said that, I think they shouldn't be copyrighted really, and the door is open for expensive litigation by larger companies shaking down smaller ones with this ruling.

As far as hijacking an API goes, well anyone is free to fork an MIT-licensed project, doesn't mean that it will gain traction.

Most of computing is built upon previous work so claiming originality in an API... well many more clever people than me have left their discoveries open to the public, and I suspect that any API originality doesn't measure up well against their work :)

Nothing is fair use until a judge rules as such in a court of law. So to answer your question: Probably, but it would have to be litigated.

This!

The hardest thing for competing chip manufacturers to overcome in the deep learning world with is the CUDA APIs / CuDNN API etc.