> After the claims Oracle made during the Google trial (such as APIs and method signatures being patent-able),
Copyrightable.
> it is clear that one can't work on the Java platform without infringing Oracle's IP.
That's not at all clear. After the third time Oracle v. Google gets ruled on by the trial court, it will undoubtedly be appealed to the Federal Circuit again. Whatever happens there, it is likely at least Google (given how the Federal Circuit has constrained what must happen at the District Court in the prior Appeal) and possibly Oracle will attempt an appeal to the Supreme Court. After that (whether the Supreme Court hears the case or not, but especially if they do), then what the law is in this area may be clear. Until then, all that is clear is what the Federal Circuit’s view of Ninth Circuit case law is, which as precedent is binding on no other court (any court bound by Ninth Circuit case law is bound by the actual case law of the Circuit, not the Federal Circuit’s interpretation of it) and, for litigants, has predictive power only for cases with patent claims that also raise similar copyright issues, and which arise out of districts in the Ninth Circuit.