JBoss MQ was the JMS implementation shipped with Enterprise Application Platform 4.2. Since JBoss Messaging is compatible with both JMS 1.1 and JMS 1.0.2b, the JMS code written against JBoss MQ will run with JBoss Messaging without any further changes.
JBoss Messaging has no wire format compatibility with JBoss MQ. It is therefore necessary to upgrade JBoss MQ clients with JBoss Messaging client JARs.
Although JBoss Messaging deployment descriptors are similar to JBoss MQ deployment descriptors, they are not identical, and will require some simple adjustments before they will work with JBoss Messaging. The database data model is completely different, so JBoss Messaging should not be used with a JBoss MQ data schema, or vice-versa.