Good grief. Which have not been exploited? All unix derivatives came from the same set of (originally open) base code, they shared nothing. They all died (to first approximation). All TCP implementations in the early days were copies of the BSD code. They shared nothing. Does Apple contribute back to Mach or BSD the stuff they do with Darwin for iOS? Does Microsoft publish their modifications to their BSD-derived networking stack?

Can I get a buildable kernel tree for my Android phone? Yup.