So I guess if I'm using JBoss is there a way to configure a datasource for Envers to use?
using JBoss or not doesn't really have an impact here.
For the time being, you can't use a different database for auditing, as Envers by default uses the same session as the one you use to read data from the database.
However adding such a capability shouldn't be very hard. Maybe you would be willing to contribute?