<p>As far as i know the EAP editions of JBoss Application Server (AS) are just a bunch of community edition JBoss projects with some sugar.</p>

<p>So, what is the <strong>community edition</strong> of the JBoss Application Server that <strong>JBoss EAP 4.3.0</strong> corresponds to?</p>

This response is really late but I came across the unanswered question in a Google search and I wanted to make sure there's a correct response.  I work for JBoss support so you can consider this a qualified answer.
JBoss EAP is the only commercially supported version of JBoss.  It contains JBoss AS and JBoss Seam.  EAP diverged (in terms of the svn branch it's built off) from JBoss AS around version 4.2.1 (not exactly, but close enough).  EAP has a 5-year lifetime and is tested and certified rigorously.  EAP has paid commercial support and patches (called CPs or cumulative patches) that are designed to maintain ABI/API stability over time while allowing for security issues and bugs to be fixed.  It is actually against policy to introduce a feature in a CP, but it happens on occasion.
If you're familiar with how
Red Hat Enterprise Linux
differs from
Fedora
, you can consider the difference to be quite similar.  The JBoss project/product split is much newer, though, so the differences are smaller.  Here's the official page describing what I've said.
http://www.jboss.com/products/community-enterprise
Cheers,
Chris