>Does anyone have any idea how much of the available PAM code is BSD
>licensed versus GPL or other?

Looking at freebsd, they have

lib/libpam from Juniper Networks - BSD license.
contrib/openpam from Networks Associates - BSD license.
contrin/pam_modules/pam_passwdqc - pick any license you want it seems.

So looks like there's enough PAM stuff that's BSD licensed to get started.

--sjg