Not just reimplementing. If you for instance have to call an external service and you mock their API for testing then you've violated copyright. The same thing

Not just reimplementing. If you for instance have to call an external service and you mock their API for testing then you've violated copyright. The same thing if you create a Facade for that API. Just as a matter of course everyday that you write code you are probably interacting with or creating code that violates this Copyright. * Implementing a Language Spec? Copyright violation. * Mocking an external service? Copyright violation. * Wrapping a library call? Copyright violation. The ability treat an interface as a distinctly different thing from an implementation is core to what we do in our jobs everyday. And the importance of being able to use, wrap, or mock out an interface without fear of legal jeopardy is essential to being able to do the work that we do.