Originally Posted by Calchas

This is true on the iPhone and at the consumer end, and for mobile hardware, but it isn't true at all for their desktop products and software.

MacOS and iOS are based on the Darwin kernel, essentially a flavour of BSD, which Apple continues to maintain as an open source product; then you have developer tools like Clang/LLVM, to which Apple is a major contributor in terms of developer time. Apple is a major force behind WebKit, an HTML renderer, since they use that in their Safari web browser; and this engine was actually forked by Google for their Chrome browser.

www.apple.com/opensource