To clarify Howard's answer: For JBM 1.4 we try and keep releases compatible but we make no guarantees - sometimes we have to fix bugs or other components need to fix bugs (e.g. JBoss Remoting) which requires incompatible fixes. For EAP CP releases, the rules are stricter and we are required to maintain compatibility between them unless there is a critical bug whose fix requires compatibility is broken. JBM 2.0 is *very different* to JBM 1.4. There is no compatibility between 1.4 and 2.0 View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4242758#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...