Correct, everything is on godaddy.
The plugin enables the user using roundcube to change their password from their webmail.
Here's part of the instructions it comes with:
*1. Configuration
*2. Drivers
*2.1. *Database (sql)
*2.2. *Cyrus/SASL (sasl)
*2.3. *Poppassd/Courierpassd (poppassd)
*2.4...