To implement DC CAL is required?

Dear All,

*I have a windows 2003 server (Std. edition) with 5 CAL (Client Access License),
*I have 100 user in my network

Now i wanted to implement the active directory in my network so is it necessary to have 100 CAL (Client Access License) installed in each and every client machine.
or can i take client machine under domain without having CAL?

Waiting for your Valuable Reply.

Thanks,
Umesh