JBoss is services based. You get EJB, Servlets etc as services. You can turn them off if you don't want them.
When you start JBoss, you can access the jmx console at:
The console will give you a good idea as to what services are deployed.
and is it possible to launch JBoss services from an application. Or I must use the run launcher? In this case, how to select which service to turn on or off? using jboss-service.xml?
You can invoke operations on JBoss services from external clients. Look into the admin guide (page 179) for an example. You will have to use the Detached Invoker framework.
You can turn on/off services in the jboss-service.xml. But if there are any custom services that are deployed in JBoss via sar files, you will have to remove the sar files from /server/default/deploy directory.
I suggest reading the JBoss Admin Guide.