Unfortunately the README of that module says:

Don't Use This Script to Change /etc/passwd or /etc/group !!

The file formats are different. You will destroy your system if you try it.

The Script Doesn't Handle NIS, POP or System Passwords

It's designed for updating passwords on the Web only. If you want to allow users to change their POP, NIS or system passwords via a Web interface, you're going to have to roll your own.