Are you sure that the first line is for JBossAS? I don't think that it will run in 30M of memory.
The second one uses up to 500MB of heap space (actual memory usage is somewhat higher because the JVM also needs some memory to do its work.
What memory usage are they seeing? If it is 700MB, I would not be concerned. If it is 3GB, then there is a problem.
Regarding tuning, see http://wiki.jboss.org/wiki/JBossASTuningSliming, and the Performance Tuning forum also contains many suggestions.
And no, it is not secure right out of the box. See http://wiki.jboss.org/wiki/SecureJBoss