This Naggregator package expects a PostgreSQL Version 8.x database backend.
The PostgreSQL-bound Naggregator instance can be downloaded from the download section of the sourceforge.net page.
To configure a working PostgreSQL-bound Naggregator, you have to setup a Postgres database and configure the mail settings in the EAR file.
After these modifications, you can deploy the EAR file to the deployment directory of your JBoss server (e.g. $JBOSS_HOME/server/default/deploy). Open your browser and have a look at (assuming a local JBoss installation) http://localhost:8080/nag-web-jsp/user/entry/welcome.