There isn't really a definition at all of what makes something eligible for copyright protection. What is and isn't covered is fairly arbitrary and informed more by history than logical derivation. Source code is typically viewed as a literary work and I see no reason API documentation would be viewed any differently.
> Following that logic...
I never said it had to be perfect, just that the reason for using the API is for interoperability -- WINE is exactly that. It allows software that was designed for Windows to run on Linux.
It's not the API documentation that's at dispute here. It's literally the abstract "structure, sequence, and organization" of the API. And there's tons of ninth circuit case law that sso isn't copyrightable.
> I never said it had to be perfect, just that the reason for using the API is for interoperability -- WINE is exactly that. It allows software that was designed for Windows to run on Linux.
What's the test here that a court can use to make that distinction? And just letting you know at one of my former jobs, we modified our codebase to better run on Wine a few times.
A creative work that takes skill isn't the definition of what should get copyright. For instance sewing patterns and recipies aren't granted copyright.
> My controversial opinion is that Google's use of the Java API wasn't for interoperability.
Following that logic, then any even slightly incompatible implementation wouldn't be legal. For instance WINE isn't a perfect recreation of Win32 by any means.