RMI is a technology which can work over two different network protocols: JRMP (Java Remote Messaging Protocol) or IIOP (Internet Inter-ORB Protocol). IIOP was designed for CORBA, and is commonly used by J2EE application servers.
By default RMI will use JRMP, so you don't have to worry about the "You must use RMI over JRMP (do not use IIOP)" restriction. That restriction is there to stop those who are used to using IIOP.
Just make sure you do not use the -iiop parameter when running rmic, and you will be fine.