There was a question regarding whether an API could be copyrighted which was never answered by the Supreme Court. The last decision in that case regarding the topic was that they could be. A jury ruled that the use of the copyrighted API constituted fair use. A federal court then overruled that decision. The Supreme Court didn't rule on the copyrightability of the API because they decided even if it was the use by Google was fair use.
The comment I replied to implied that something couldn't be fair use if the use was commercial. Google's use of the API was commercial and yet ruled fair use by the highest court in the land.
I hold that whatever is fair use for an API is not even close to what is fair use for the source of actual implementation, let's see what the court has to say on that.
