Description of problem: A new version is available on GitHub. The change is that now it's Maven'ed and with some small changes: https://github.com/java-schema-utilities/relaxng-datatype-java/tree/relaxngDatatype-2011.1
I changed the gid:aid to use the old relaxngDatatype and WildFly seems to work. I have no idea how stable it'll be.
Fixed in F22+