JBoss is J2EE compliant, perhaps the most compliant available App-Server :-) See certification under http://www.oracle.com/technetwork/java/javaee/overview/compatibility-javaee5-jsp-141098.html
Like all J2EE-Servers also JBoss AS has some non-standard features (like jboss-*.xml/-ds.xml/-service.xml-Files), in which you can configure additional stuff.
The all-Template contains a well configured Cluster-Template, but you need in each case a customization of the current config-files. You also could take the minimal-Template and add needed deployers and config Items to build your own Cluster - this would take sure a bit more than 10 minutes...
You'll find additional Information about Class-Loading at http://community.jboss.org/wiki/jbossclassloadingusecases and http://community.jboss.org/wiki/classloadingconfiguration
Hope I could help you. Best regards,
Additional to Mark's hints, JEE compliant is to use 'call by value' which is used by the standard configuration, but the optimization is to use 'call by reference' for a better performance.
This is quite useful, but indeed not conform to the JEE spec and you must respect it in your code otherwise you might have unexpected results.