Pretty wild that MAME has been under active development for over 28 years with the core concept unchanged and no serious forks. It must have a very committed dev community.
constant slap fights between contributors (usually involving haze or guru)
important PRs left ignored due to internal drama
8GB+ memory leak during building that they're in no rush to fix
Haze is almost always in conflict with mame lead Cuavas when trying to upstream his code, but his anger mostly justified.
Cuavas is a huge micromanager, he won't accept your code even if you just missed a typo in a line comment.
I respect his commitment to hold the codebase to absolute standards, but sometimes he takes his micromanagement too far that just makes the whole process unproductive.
Edit: Found the quote. The Right to Merge is about the maintainers right to merge your fork/changes back to their branch. Not the other way where random dev have a right for their changes to be merged into the original project
I also won't be naming any of them because those "committed" mame devs are very quick to inject themselves into any story about them, and harshly judge everything else that touches their code that didn't come from them.
Has its pros and cons, of course.
What about Final Burn Alpha/Neo? They're extremely popular.
They do share some CPU emulation code, but that's common in emulation, often someone wriets a good CPU core then it gets passed around.