Actually Google kind of screwed themselves there because just this year they set the legal precedent that all APIs are public domain so if they sued they would lose the case against oracle(and 8.8 billion dollars).
However, just having an API to follow does not mean, that the task of reimplementation is easy - following someone's else API is actually harder than designing your own. Just ask the WINE team.
Google won on fair use.
LOL Really? A likely win? The CAFC isn't going to overturn a jury verdict.
According to the CAFC's ruling overturning Judge Alsup's initial decision that APIs are not copyrightable, APIs have enough unique expressikn in them to indeed be covered by copyright. Hackers are fond of a loosey-goosey, asterisk-ridden interpretation of copyright law under which copying is OK provided the author doesn't lose money in its primary line of business. (For example, that pirating abandonware is OK, etc.) The CAFC is considerably more strict and applies the letter of the law to copyright cases. While fair use is a concept ill-defined by statute, it is generally acceptes to mean extremely limited copying for express purposes, such as: scholarship, commentary, or parody. Google's copying of Oracle's Java API IP was extensive and directly related to their Android line of business. Therefore, any sensible court would rule that fair use doesn't apply, else American IP law has no meaning.
Frankly, everything else would be a travesty.
My personal wet dream is that in response to this, Google will partner with Microsoft to get dotNET as a VM backend.