I believe HA JMS was included in the 3.2.3 release.
But it is not configured by default.
Is HA JMS just used for fail over of queues and topics or can it also be used to load balance MDBs?
I understand the 3.2.3 HA JMS to be a singleton cluster (i.e. you have one master message queue; if the master fails, then a new master is elected).
See http://www.cocoonhive.org/articles/jboss/20031125/JBoss32-hajms.html for more guidance.