if you are looking for Red Hat supported and certified configurations take a look at https://access.redhat.com/site/articles/111663
but if you are just interested if it will work that is different story.
Jboss AS7 (EAP6) basically has only dependency on JDK 6, and any system that runs that should be able to run app server.
so you can choose any OS/HW combination you like as long as you have proper version of JDK.
I would contact Brian May whos responsible for the Sandbox at http://www.youngiprofessionals.com/ .
I'm sure It will run on IBM i and of course better than on any other platform.. :-)