The "reimplementing" of the API is not the subject here. The use of the same API is. Google does claim they performed a clean room reimplementation. Oracle tried to say Google stole their code, but after building custom software to look for copied code they found a single 9 line function that they claimed was copied out of 15 million lines of code. Having nowhere to go with the code copying claim they came up with the 'But you're using my API!' nonsense. Many APIs have been reimplemented all over the place, win32 alone has been a few times.. this has always been assumed to be okay.

According to this tweet: http://twitter.com/taviso/status/16005411316 Those 5 days were spent trying to negotiate a fix within 60 days. So much for the 'he only gave them 5 days!' arguments.