All the competing Unix forks? The infighting in the Unix world and the blatant attempts to break compatibility with each other pretty much killed Unix, about th

All the competing Unix forks? The infighting in the Unix world and the blatant attempts to break compatibility with each other pretty much killed Unix, about the only thing keeping it limping along any more is all the effort that's been put into OpenBSD and FreeBSD, and the commercial backing for Solaris. Edit: Just realized you said non-hostile. Yeah, not so much, prior to GitHub most forks that weren't to try to take ownership were either experimental in nature, to continue development on an abandoned project, or in order to develop some features that the original authors disagreed with (semi-hostile). I'm not sure you can classify picking up a dead project as a hostile action, but it isn't exactly benign either. As for experimental branches those were usually non-hostile, but at the same time if they bore fruit they would typically get merged back into the upstream so not really a fork in the truest sense of the word, but more like a really long running branch.