This happens all the time. It's called a fork.
Forks happen for good reasons, bad reasons, dumb reasons, and smart reasons.
Sometimes the useful changes can be shared back, and that's a good thing
[for that situation].
Sometimes changes cannnot be shared back, and that's also a good thing
[for that situation].
Can only be answered on a case-by-case basis.
The reality OF THE CODE is such that *BSD and Linux share good SOLUTIONS
quite often. That's a benefit of open source. And that's a good thing.
Jeff
-