New database or New Schema?

In the next release of our software the developers are moving to JBoss and
have introduced the use of JBoss Messaging. They want to change from using
the built-in hsqldb to using our PostgreSQL database.

What is the best approach, create a new database or new schema with-in our
current PostgreSQL database?

I'm leaning toward creating a new schema as we already have built-in
procedures to backup and restore the application database.

Thanks,
Eric