This package uses jars from several of the jboss-module-* packages, which are only available from java-experimental. I see in bug 188356 that this package was recently moved to java-overlay to enable building spring, but the spring-2.0_rc4 ebuild specifically depends on the 3.0 version of hibernate-annotations, for which there is no -bin package, so it can still not be emerged.
Still no news on this?