It can. Depending on which 2003 CALS you buy. There are 2 types of CALS. Device CALS, and user CALS. The difference between the 2 are device CALS only apply to devices on the domain, ie., you can have 4 PC's and 1 server (if you have 5 CALS), and not worry about the amount of users. For user CALS, you can have 5 users (with 5 user CALS) and not worry about the devices.
It all depends on which way you want to go.