The best way to keep up with the latest changes to our project is to download the code from Subversion, and keep a constant monitor on the mailing lists.
Although we run continuous integration tests, the trunk is occasionally unstable and sometimes may not build. If you wish to build from Subversion source the latest tag is:
http://anonsvn.jboss.org/repos/labs/labs/jbosstm/tags/JBOSSTS_4_2_3_SP7
For all tagged versions use http://anonsvn.jboss.org/repos/labs/labs/jbosstm/tags/ and pick the one you want.