I just read most of the majority opinion, and a little bit of Thomas-and-Alito's dissent. The majority opinion says basically "we're going to assume for the sake of argument, without actually asserting, that an API is copyrightable, and concentrate on the fair-use question. [pages of argument omitted] Since we find there was fair use, we don't need to address the copyrightability question."

The dissent, rather oddly (to me; IANAL), criticizes the majority for skipping over the question of copyrightability, and spends some time asserting that an API is copyrightable. It then claims that Google's use was "anything but fair"; I haven't waded through their reasoning for the latter claim.

Anyway, yay! Not because I work at Google, but because I'm a software engineer who appreciates the idea that one interface can have many different implementations.