First of all, you need the JEMS release of JBoss for this to have any hope of running. Make sure that is what you got. 4.0.4 GA will NOT work.
Download the release here:
Use that, and see if it works.
You don't need to download Seam separately. When you install, make it install the EJB3 configuration (I'm pretty sure that's what you need).
Thanks a lot. Follow your way, it's OK.