I wouldn't celebrate a victory yet. As is often the case, the court's choice of tests simply will serve as a blueprint for others on how to avoid themselves being caught in the same kind of result.

Based on this court decision, it's apparently fair use to lift someone else's API and use it to jumpstart programmer familiarity with your product, if the author of the API previously tried to achieve success in that narrowly-construed, retroactively-interpreted exact same market segment and wasn't very successful.

I see a few things coming out of this. IP holder companies will become even more common: they will be used to hold copyright to one API and license it out to customers -- including independent companies that you would currently recognize as part of the same platform.

But because the IP holder does not provide an implementation and therefore does not 'compete' in a market segment, any unlicensed use of it is necessarily infringing: there's no innate functionality with which one can interoperate under the doctrine of fair use.