Hello, could someone help me please:
As I know Catalina is the built-in JVM of Tomcat. Does JBOSS use Catalina or use SUNs JRE/JVM for Tomcat? Also, can it be changed from one to the other?
You are misinformed. There is no built in tomcat jvm, and catalina is just a code name for tomcat 4. The jboss server whatever jvm you configure via the JAVA_HOME environment variable.