Blueprint describes the thing that is to be built. API describes how two parties talk to each other.

I'd say API is closer to a protocol or a contract than it is to architectural blueprint.

My understanding is that QWERTY was developed to solve a mechanical problem with early typewriters in the 19th century (frequent jams). According to wikipedia the inventor spent 5 years developing it. I don't see why he shouldn't have been able to profit from that invention. The only reason we use QWERTY now is due to the fact that early non-mechanical keyboards were designed to be used easily by people who had trained with mechanical ones. If "licensing fees" for QWERTY back then had been an issue, manufacturers would have just used a non-copyrightable ABCD... layout, or paid for QWERTY. I don't see it as a disastrous outcome.

Even if independent derivation is a valid defense, with Oracle setting a precedence, people would be taken to court all the time, and what is considered trivial becomes a matter of opinion. It won't be long before the whole situation devolves into automated takedown of GitHub code by big corporations.

Ideally, we shouldn't even have to go to court to begin with.