Someone will eventually have to answer the question of why this is better than using LDAP, PAM, and/or kerberos. Those are all open standards and well known by a large population of *nix SAs.
Another standard to consider is ACAP, currently supported by Eudora and Mulberry (both IMAP email clients).
<http://asg.web.cmu.edu/acap/>
Mulberry also supports something called IMSP:
<http://cyrusoft.com/support/faq/mulbpapers.html>
