Why did they decide to fork OpenBSD?
OpenBSD is an amazing project and has some of the best code around but some of us are of the opinion that it could use a bit of modernization. OpenBSD is a very security conscious project and, correspondingly, has to be more conservative with features. We want to be less restrictive with the codebase when it comes to experimenting with features.
http://bsd-beta.slashdot.org/story/12/06/13/1645211/openbsd-...
I'm not sure why I would use a fork of OpenBSD instead of just FreeBSD though. I've always seen the primary benefits of OpenBSD as deriving from their obsessive focus on security, but if this fork isn't focussed on that I'm not sure what I gain vs. other BSDs that already have these goals and objectives in place/completed.
It would be interesting though if Bitrig became sort of a DragonflyBSD for OpenBSD, where weird experimental stuff can be tested in a separate playground.
It is you who say "instead", can't it be "in addition to"?
Why wouldn't they start with what they already know, find good, and are happy to work on?
It'd be easier to carefully add specific features to a well-designed and secure codebase such as OpenBSD, rather than try and pare down and audit the huge codebase and large amount of features provided by something like FreeBSD.
Looks to be a desire to leave behind legacy cruft, add a better toolchain, and add virtualization.