JBoss ESB is 100% Java so should run on AIX.
As far as Weblogic & Websphere go, JBoss ESB 4.2.1 GA can operate in its own container that is not a J2EE Application Server that sits "beside" WLS/WAS JVMs but not "within".
Great... thanks for the feedback.
Don't believe everything you read on wikipedia either. AFAICT we had nothing to do with that page.