Like you said fair use applies to copyrights. The question in the google case is if the API can actually be copywritten. Assuming google did a perfect cleanroo

Like you said fair use applies to copyrights. The question in the google case is if the API can actually be copywritten. Assuming google did a perfect cleanroom implementation of parts of Java and they lose this case then it can be assumed that cleanroom implementations offer no protection against copyright claims. A lot of non-commercial projects get shot down by companies for copyright infringements. Being non-commercial won't protect you either.