The current holding that APIs are copyrightable, and reimplementing them for interoperability is not fair use.

This is in direct contrast to decades of consensus that APIs are not copyrightable, and furthermore, there is a particular procedure to go through [clean room technique, which Google did] to ensure that the API is reimplemented without infringing any copyright.

Letting this ruling stand would mean that nearly every piece of software you use infringed someone's copyright.

Ah, gotcha - so the Court of Appeals for the Federal Circuit* decided in favor of Oracle in this case. Thanks for taking the time to type that out, I've been living under a bit of a rock it seems!

*corrected from "second district court"

The CAFC, not the second district.

Pretty much what jcranmer said: The status quo, for decades, has been that you can do that. So this would be a drastic change to the rules by which we play the game.

More: Recall that copyright lasts close to forever. (95 years for corporations, if I recall correctly.) This ruling, then, would have allowed IBM to sue every BIOS clone maker, and keep a stranglehold on the PC market, and still have that stranglehold to this day, and be able to keep it until 2076. Then, on August 2, 2076, then we could get IBM-compatible PCs.

Compare that to actual history, and you can see why I think the current ruling is horrible.