I know they didn't start those, but they all have major contributions from Apple.
Apples builds of Clang and LLVM are not open source by default.
Edit: No amount of downvoting makes me wrong, they aren't open source. The AppleClang != Clang trunk
Sure, but that’s deeply misleading since Apple contributes most of their code to trunk. The fact they ship private builds for their own machines is a complete red herring.
WebKit is a fork of KHTML and the source had to be released in order to comply with the LGPL.
Sure - just like anyone else who contributes to LGPL projects, Apple willingly chose to do so.