This page describes how to deploying ESB 4.x archives on JBoss AS 5.
Deploying Non-Scoped Deployments
Deploying an ESB 4.x archive should simply be a matter of adding the .esb archive to the deploy directory.
With AS 4.x one could specify that a .esb deployment be scoped by adding the loader-repository element to deployment.xml. Starting with JBoss AS 5.1.0 a scoped deployment should instead be specified using a jboss-classloading.xml file to the META-INF directory of the .esb archive.
So, if you have a deployment that is scoped add a META-INF/jboss-classloading.xml that looks something like this:
Some more background about why this is needed can be found in this thread :