Wine would be a much better example of fair use. It is explicitly made to allow users of linux to run programs written against win APIs. It is not so clear in the Oracle vs Google case, because it is questionable whether Google’s case was really fair use (google pretty much didn’t want to pay Sun for the mobile license and the whole thing was done as cost saving) - hence the very long timeline of the case.

The dissent explains how Android fails three of the four fair use tests. I'm not sure what the majority was smoking when they wrote this, but far better examples of fair use exist, especially uses that are noncommercial and especially are noncompetitive with the original.

Java was a mobile OS before Android literally obliterated the market after copying Java. Arguably, if Android was fair use, everything is fair use and all software copyright is fundamentally defeated by this ruling.

I think Thomas makes a mistake in disregarding the reason for introducing the distinction between declaring and implementing code. The law (as I understand it - IANAL) doesn't exhaustively enumerate what does and does not constitute fair use. Therefore, any specific instance of fair use is bound to introduce new distinctions that are not specifically mentioned in the law itself.

In this particular case, Google's copying of interfaces was ruled to be fair use because its purpose was to allow Java developers to reuse their skills. This reasoning only holds for the declaring parts of the copyrighted work though. And that's why the distinction becomes necessary even if Congress rejects it as a primary distinction between copyrightable and non-copyrightable work.

That's also why I think the ruling is perhaps not quite as broadly applicable as some (including Thomas) are thinking right now. It may not cover code that isn't used by a significant number of developers. I haven't read the entire ruling, so I'm not sure whether it covers non-public interfaces that are nevertheless useful for interoperability. Such interfaces were at the center of past disputes (I think Microsoft's SMB protocol was one such case).