if you want save, the best way (IMO) is to put all in an EAR-File.
So your application work with the necassary XSLT and JBoss and other applications in the same JBoss AS runs with different..
I have already tried that.
I put the three jars in my .ear file, and declared them as java modules in the ear's META-INF/application.xml, as I do with several other libraries used, but it does not work. I get the same error as I get when running with the old jars only.
One thing you can try (if you are using jboss-3.2.5 or above) is set the isolated property on EARDeployer to true so that your EAR has a scoped classloader. If you are using a earlier version, then you can always set scoped class loading for your ear using jboss-app.xml. Check the jboss docs for Scoped EAR Loading.