Adapted from a private email:

HEAD/M4 branch require at least JBOSSAS 4.0.3SP1 -- PATCHED WITH -- EJB3-RC5-PFD (http://jboss.org/jbossBlog/blog/bburke/2006/02/02/JBoss_EJB_3_0_RC5_Released_minor_fixes.txt)

possible solutions:
1. You MIGHT get it to work with JBoss 4.0.4RC1 that was just released. This SHOULD work but I haven't had time to try it. (Will soon)

2. You MIGHT just grab the EJB3 RC5 release and patch your JBAS 4.0.3SP1 with it (this is what I did)

3. The EASIEST route is to just download/install today's M4 release and remove mail.ear (the actual JBMS part) from deploy. This will essentially be MY copy of JBAS403SP1+EJB3RC5-PFD slimmed to just "default".

I need to make clearer instructions but this change just happened and I was working on getting a stable milestone out (because M4-pre1 leaked database connections due to bugs in the EJB3 that came with 4.0.3SP1)

Always use ANT to build, never use eclipse (except for its Ant integration). There is an eclipse project file in CVS. set the JBOSS_HOME in the libraries off of the project properties.