Is JBoss Enterprise App Platform a commerical fork of JBossAS?
Is it a super of subset of JBossAS?
Is there a side-by-side comparison of the included tools?
Go to http://www.jboss.com/products/platforms/application/ and download the datasheet. Look at the "Components and Features" section.
In a nutshell:
EAP 4.2 = AS 4.2.0 + Seam + patches
EAP 4.3 = AS 4.2.1 + Seam + JBoss Messaging + patches
EAP 5 = AS 5.1.0 + Seam (this is from my understanding, still waiting for my trial copy)