There's a Gentoo mailing list thread that's still active about this fork. "It is no secret that many of us are unhappy with the direction that udev has taken under the leadership of the systemd developers....After speaking with several other Gentoo developers that share Linus' concerns, I have decided to form a team to fork udev. Our plan is to eliminate the separate /usr requirement from our fork, among other things. We will announce the project later this week."
Linus Torvalds has also recently criticized udev with comments along the lines of the code maintenance going into "crazy mode" and "they have made changes that were known to be problematic, and are pure and utter stupidity."
The Gentoo fork can be found on GitHub as udev-ng.