IMHO this is just a organisational issue because the posibillity of errors is not really different.
We decide to separate complete to avoid confusion.
We also have your own start script and store the PID of the JVM and a customized installer to adapt JBoss and add our app.
Duplicate the server (BTW I'll allways use my own config insted of default/all/etc.)
- will save disc space (which is not expensive)
- can error prone for stop/restart
- more effort in case of JBoss library updates (JB 5.1 use a common lib folder, JB4 a server/XY/lib)
- no difference whether same or other system
Is there any impact on the server resources?
nevertheless how you start each JBoss instances is started with its own JVM.