And to get back to your original question - In theory it should be possible to switch back to JBoss Messaging in JBoss AS6. Infact, up until some specific milestone release, JBoss AS6 used to ship with JBoss Messaging. However, it would need some efforts to make sure that you configure JBoss AS6 with the right set of JBoss Messaging configurations and jars. I don't think anyone has tried this against AS6. So I won't be surprised to find no documentation on how to do this. So it's going to be a trial and error effort.