Currently, Seam 3 does not run on Java 5, only on Java 6 and above.
  https://issues.jboss.org/browse/SEAM-126

Do you have a use case where you use or going to upgrade to Seam 3 in Java 5 environment?
If so, please comment to this thread, we're trying to asses how big the userbase is that still needs Java 5 compatibility in Seam 3.