The Linux kernel definitely has the interest to force people to upstream modifications. GCC rejected the idea of converting itself as a library to force vendors to upstream their changes.
If something is "forced", it is inherently not an "invitation".
Additionally, GPL and derivatives focus on sharing code with users, which isn't necessarily the same thing as collaborating with the project's creators upstream. It depends entirely on how and where the software is used.
Additionally, GPL and derivatives focus on sharing code with users, which isn't necessarily the same thing as collaborating with the project's creators upstream. It depends entirely on how and where the software is used.