The core engine itself is a simple Java component so can be integrated in any application by simply adding all the necessary jars in the application classpath.
If you want to use the jbpm-console, the artefact you can download is configured so it works by default on JBossAS 4.2.3. Updating to another application server usually involves updating the configuration files to the new setting and making sure the necessary dependencies can be found by either adding them to or removing them from the WEB-INF/lib folder (as the default classpath can be different in different application servers).
As part of the productization process, we will definitely be testing the deployment on other versions of JBossAS and Tomcat for example.
Do you have any specific issues when you for example try to deploy the jbpm-console wars to Tomcat?