JBoss AS2? this might be a EJB1.0 or 1.1 application.
If you use JBoss4.2 you might be able to run the application after you reassemble the archives.
I suppose that JBoss4 suppose the ejb-jar is of EJB2.1 and that might differ to the old style.
Also I know that there are some changes for the CMP container that might be problematic for the application behaviour.