Have a look at: http://wiki.jboss.org/wiki/Wiki.jsp?page=Running2.6UnderJBoss4.2.x. While the information is for 2.6, it might work as well for 2.4. As far as I am aware, there are no plans to support 2.4 on 4.2...
Thank you for the reply. Not only did you answer my question, but the one I was about to post :)