> Define rarely? What about Webkit, LLVM, and CUPS? These were already established opensource technologies. Apple has improved these technologies. But LLVM, Webkit or CUPS would exist even if there was no Apple.

Erhm, "established" yes, but with a very small base. LLVM was an academic project - Apple hired Lattner to form a team and fund the development of the project.

WebKit was not established, Apple forked it from KHTML and it would not be the dominant engine without Apple.

Let's also not forget that BSD would be a rare sight at this point if not for Apple.