Whether non-copied code imported via PHP's include() statement is covered by the GPL is up to the lawyers to decide, but personally, I'd say if your code explic

Whether non-copied code imported via PHP's include() statement is covered by the GPL is up to the lawyers to decide, but personally, I'd say if your code explicitly calls GPL'd functions (as opposed to via a callback or so) or subclasses GPL'd classes, you're asking for trouble. If your code happily runs outside WordPress, you have a much better argument.