[jahewson]

What I mean is that there is no written law containing the words "clean room", and no requirement that an author has not seen similar works. While "clean room" might be a good defence, there aren't automatically grounds for making an infringement claim just because somebody hasn't followed such a hyper-cautious practice.

Oracle vs Google is complex and I reluctantly chose to gloss over the details. The case still has some appeals to go yet, posssiby to the supreme court. While the difference between APIs being copyrightable vs fair use is important, the practical impact should be negligible: if an API as large as the JDK can be copied without permission, then any API can.