Nope, Seam only works with Java 5 and above. Taking this stance is a very important part of Seam's identity. The Seam developers intentionally decided not to cater to an outdated (and broken) version of Java. Instead, Seam presses on and takes advantage of what Java has to give you a better development environment.
Seam uses:
lots of annotations
the improved concurrency model
the
thread dispatcher
generics (Seam Application Framework)
