It would need a version of Seam written for JDK 1.4, with all annotations as regular old Java interfaces. The same for Hibernate Annotations, and all of EJB3. It's possible, but not doable. (Unless you are volunteering to maintain that ;)
Also, what could possibly be the reason to say "I want to use cutting edge stuff like EJB3 and Seam, but I want to give JDK 5.0 a few more years to mature"?
Yes, JDK 5 went final when? Two years ago? Something like that?