Why would somebody fork Haiku? A full fork is unlikely to happen unless there's really significant technical or cultural differences that can't be resolved within a single code base and community.
There was a short-lived fork _years_ ago that used the Linux kernel instead of Haiku's kernel. I don't even think the fork was made publicly available due to the community backlash.
Community backlash? Could you explain more? I have never heard of this before, and I am unsure why the Linux kernel would be the source of controversy as you describe it.
Humor me; when has that happened? Off the top of my head - Open Office is still dead, netbsd and openbsd are both fine but I don't think the fork played into that, neovim gave vim a kick but they'd stagnated and Haiku hasn't... actually, that's a trend; forks help when the original has stalled, but Haiku is healthy and happy to take contributions.