Xenocara is the name chosen for the version of X included in OpenBSD. It is currently based on X.Org 7.6 and its dependencies.
The goal of Xenocara is to provide a framework to host local modifications and to automate the build of the modular X.Org components, including 3rd party packages and some software maintained by OpenBSD developers. It is not a fork. We are tracking X.Org modifications and try to push back our changes whenever they are good for upstreams too.
To learn more about Xenocara, read this old article on Undeadly or listen to that BSD Talk interview.
Official binary snapshots are available as part of OpenBSD-current for most architectures.
The source code can be browsed using OpenBSD's cvsweb server.