JBoss AS EAP versions - What parts of EAP source code are closed source?

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http://serverfault.com – Question about the source code for JBoss EAP versions 4 5 or 6. Let's say we decided to purchase JBoss EAP 6 from RedHat. Can we still run maven to build JBoss EAP version? Are there closed source resources involved? Basically we are worried that going with the EAP version will limit our ability to utilize JBoss as an Open Source tool. I would imagine there is closed source involved. Otherwise, for example, people would be able to take the patches from JBoss EAP 4.3 and then apply them to JBoss 4.2.3.GA community version. Or am I mistaken? Please see this reference: JBoss Enterprise App (HowTos)