The Google v. Oracle decision raises an interesting question.
My understanding is that a proprietary application which dynamically links to a GPL-licensed library is considered a derivative work and has to distribute its source along the binary.
However, what if said application could load any DLL that conformed to the GPL'd library API, based on a user-specified configuration (or placed into a specific location)?
The vendor of the application could even provide a stub implementation with basic functionality and low performance, and let the users replace it with the GPL'd library "should they wish to do so".
The vendor is off the hook since the application they distribute does not contain any GPL-licensed code, and does not technically require it.
The users are off the hook since they don't distribute anything, and the GPL places no restrictions on use.
It sounds like a loophole to me. Am I missing something?