The program is designed to run as a service on Windows Server 2003, using ActiveDirectory as authentication and authorization (and, if I ever bother to complete the code: accounting) backend. It translates AD group membership (memberOf) to the NS-Group-Member RADIUS VSA, and, if present, uses ActiveDirectory's msRADIUSFramedIPAddress to set the Framed-IP-Address RADIUS attribute.
The comments included in the script will guide you in writing a configuration file and getting the service up and running. In the most trivial case, putting something like
DOMAIN example.com CLIENT 192.168.254.253 mysecretin a file config.txt in the script directory is sufficient; the script may then be run manually or installed as a service (using the -install switch). Try it manually first -- chances are that some of the required PERL modules aren't installed on your system yet.