> Software that implements other party's APIs might be obligated to agree to a licensing agreement - projects like Wine, Samba and various 3rd-party emulators.

> Software that implements other party's APIs might be obligated to agree to a licensing agreement - projects like Wine, Samba and various 3rd-party emulators. It's far, far larger than that. Netscape implemented the Blink tag first and other browsers followed suit. Now Netscape (or whoever owns that copyright) can sue all browsers that implement the Blink tag.