NT PDC licensing

[Adam Killian]

Greetings,

I was wondering if anyone has any experience with Micorosft's licensing policy wrt samba.
I want to use an NT PDC and some BDCs to do my username/password authentication, and use Samba for all my file/print servers.  Obviously, I will need licenses for each NT server, but if all I am doing with it is authenticating users, do I need a CAL for each user?  This is going to be a 2500 user installation, so it makes a big difference to the total cost.  If I do end up needing CALS, I will have to use some other authentication mechanism.  

As I understand it, I can configure Samba to act as a PDC, but not as a BDC. Since this will be a mutli-site deployment, that won't work.  I guess that leaves me with NIS or LDAP.  Does  anyone have any reccomendations/suggestions/horror stories?

Thanks,

Adam Killian
akillian at footlocker.com