idk, Apple does have open source? Swift is *incredibly* open, but probably a outlier for Apple. It's operating systems aren'tt, but kernal is (right?).
None of these companies are open sourcing their core competencies. Google Search isn't open source.
LLVM has been pretty import for Apple.
Webkit has been important.
BSD has been important, but afaik they don't really contribute a lot back anymore, although Darwin is open source.
