samba - Jul 2003 - affordable "mid-way compromise" with samba 3.x and M$ ADS server participation ?

Guys,

A simple question from a naive guy ;-). Would it be possible and legal, 
in terms of M$ software licensing, to use a w2k or higher (2003?) ms win 
active direcotory server as the main active directory server BUT have 
all the clients connect to the samba 3.x which runs as a pdc and has 
joined the ADS domain?

And IF this is technically possible would this "avoid" having to get
any
more licenses than the 5 (is that correct) that come with a fully 
licensed basic w2k/2003 server?

In short is there any mileage in this sort of "affordable mid-way 
compromise"?

Please don't flame me if this is the silliest question you have ever 
come across. ;-) I am only trying to survive in a seemingly more and 
more M$ dominated world. BUT am unwilling to fully yield.

Many thanks in advance,

Urs Rau