Wikipedia
Xenocara is the OpenBSD build infrastructure for the project's customised X.Org Server that utilises a dedicated _x11 user by default to drop privileges and perform privilege separation in accordance to OpenBSDs least privilege policy. The patches for applying this rather important security protection were provided to upstream for the benefit of other Unix-like systems such as Linux, however the care to apply and maintain them has unfortunately not happened to date. As some Hardened Gentoo users can attest, X11 can be run without root privileges on Linux, however functionality such as access by users to recently plugged in devices such as a USB mouse is lost.
Until release 6.9, X.Org used imake but recent modularised versions have switched to GNU autotools. Xenocara uses BSD make and is designed to ease building and maintenance of modularised X.Org within the OpenBSD CVS tree. It first appeared with OpenBSD 4.2, released on 1 November 2007.
Apart from X.Org, Xenocara builds several other projects, including window managers FVWM and cwm.