The consequence is you can't run 2 jboss instances on different configurations simulaneously. Each instance needs its own data/log/tmp dirs. In general, whatever is under a configuration JBOSS_HOME/server/xxx must not be shared across instances.
What would be the possibilities of, within a production environment, having multiple configurations running at anyone time?
All other linux servers I have seen (so apache, mysql, various ftp servers, tomcat standalone) only have support for one instance at a time. Do Jboss (and J2EE in general) servers break this mold?
As an example is it likely that a production server would run a jboss webservices capable/configured server as well as a jsp/servlet jboss server simultaniously (and separately).