Hi,
you don't need to run the demo targets. Since you already have both JBoss and Postgre you could execute following sequence of tasks:
create.jbpm.schema - you need to provide data base name -Ddatabase=postgree
load.example.identities- you need to provide data base name -Ddatabase=postgree
install.jbpm.into.jboss - you need to provide JBoss home directory -Djboss.home=YOUR_JBOSS_HOPE_DIR
install.examples.into.jboss- you need to provide JBoss home directory -Djboss.home=YOUR_JBOSS_HOPE_DIR
Cheers,
Maciej