In case anyone else is stuck on the same..
You can set the default context to
/in your application.xml - but you can only have one application set like this per JBossAS instance.
In this sense an instance is defined an actual instance (i.e. different server config folder), or a virtual host. You can deploy each of your applications to a a different JBossAS virtual host, and have them all set to context root
I don't believe there is a way of achieving this just with Apache rewrites.