1) If you have multiple IP address, you can run each bound to its own IP address as follows:
run -b localhost (for test)
run -b myhostname (for production)
Actually, you always have multiple IP addresses: localhost and the one assigned by the DNS.
2) If you do not have multiple IP addresses, you have to change the ports that one of the instances uses. See the file docs/examples/binding-manager/sample-bindings.xml.
See also http://wiki.jboss.org/wiki/Wiki.jsp?page=ConfiguringMultipleJBossInstancesOnOneMachine
I choose the second possibility.