The current production release is 1.2.9. There is no current beta release.
The next release of XOM™ will probably be 1.2.10. 1.2.10 should be backwards compatible with programs written to the XOM 1.0 through 1.2.9 APIs.
You can check out the latest XOM from CVS using the standard CVS command line client as follows:
$ cvs -d :pserver:email@example.com:/cvs login Logging in to :pserver:firstname.lastname@example.org:2401/cvs CVS password: $ cvs -d :pserver:email@example.com:/cvs checkout xom
Just hit return when prompted for your password.