They're similar to Apple in that they use open source in their private ecosystems and also contribute stuff back to the community, just not their entire product

They're similar to Apple in that they use open source in their private ecosystems and also contribute stuff back to the community, just not their entire product. Apple has open sourced Bonjour (zeroconf), Webkit, LLVM, libdispatch, etc. Github has open sourced Atom, Jekyll, have contributed to lots of Ruby/Rails projects, etc.