JBoss ESB support AS 5 and AS 6, but there are no plans for JBoss AS 7 support. If you want to use JBoss ESB, I'd suggest starting on 5.1.0.GA, or if you want to use AS 7, I'd suggest investigating SwitchYard (http://www.jboss.org/switchyard.html), which is a new jboss.org project designed to be the next major versio of ESB at JBoss.
For some more background, here's some similar threads that contain a little more of the background behind this and some interesting resources regarding SwitchYard :
thanks for your response
i'm download switchyard just now