True, but you can compare them to, say, Google, which maintains thriving OSS projects like Chromium and AOSP and generally does a way better job at publishing code and research.

I wouldn’t mention as positive example. I wouldn’t even mention them as example.

Apple cooperates within WebKit well with WebKitGtk. They supported LLVM when it is in their interest.

Chrome is used as proprietary web-engine to vendor lock-in the web. While often used by others, I’m not aware of a broad cooperation. Android is a shadow of Linux, merely using the Linux-Kernel, not GNU. Plus a lot of closed-source code (PlayServices, App Signatures, Google Cloud, Google Apps).

Googles open-source projects seem often exclusive Google only projects? Google works together with others! But especially Chrome and AOSP are…causing worries.