I am no JBoss expert but perhaps this will help. There is no guarantee that any of this will work but here goes. Do you have the jar that contains com.microstar.xml.SAXDriver? If not you need to get it and create a module for it. To do that you go to your jboss/modules folder. There should already be a com folder. In the com folder create a microstar/xml/main folder. In the main folder put your jar. Also in the main folder create a file named module.xml. If you look at any of the other module.xml files you will see that they contain the module name (path to the jar), the jar name, and any dependencies that the jar has. Create something that looks like other module.xml files. Now your application needs to declare a dependency on the module. You can do that by adding a file in the WEB-INF folder of your war. You can use MANIFEST.MF file and a line like "Dependencies: com.microstar.xml" or a jboss-deployment-structure.xml file (there are a bunch of examples on the internet) As far defining user variables I don't really know. You could read them from a properties file or I have seen a JBoss tutorial about passing variables by changing the bat/sh file that starts the server. I think that there is a JAVA_OPTS line that you may be able to add something to but I'm not sure.
I hope that this helps a bit.