I have found differences in common jar files in RESTEasy distribution and EAP.

StAX 1.0 API
===========
JAR: stax-api-1.0.jar
RESTEasy: Specification-Version: 1.0.1, Implementation-Version: 1.0.1
JBAS: Specification-Version: 1.0, Implementation-Version: 1.0

There is issue with StAX in TCK and for this reason was this lib reverted to the 1.0, please see JBPAPP-2609

Commons-logging
=================
JAR: Commons-logging.jar
RESTEasy: Specification-Version: 1.0, Implementation-Version: 1.1.1
JBAS: Specification-Version: 1.0, Implementation-Version: 1.1.0.jboss

This problem was explained by Fernando in JBPAPP-2412