[pabs3]

> why would anybody share anything

Before LLMs, it was cheaper in the long run; by upstreaming your patches you don't have to rebase them continually and sometimes the community will maintain the code for you. OTOH sometimes you might need to work on the code again though as other parts of the project evolve if the project is likely to throw out unmaintained code; this is especially true in the Linux kernel where internal APIs change constantly, but upstream maintenance is probably cheaper than continually backporting security fixes to your stable/LTS/SLTS or completely dead versions.

With LLMs the costs might be different but will still exist.