Posted 04 January 2013 - 14:17
No 2003 CALS can only be used with 2003. At the moment, I would buy 2013 CALs. You can use these with 2010, but you will save the money if you later decide to upgrade to 2013. (same with server, buy 2013 server licenses).
In terms of CALs, There are now 2 types of CAL. Standard and Enterprise. You need standard CALs to use the product, and the enterprise CAL gives you additional rights (things like archiving and advanced journaling etc.)
In terms of server licences, the ONLY difference between standard and enterprise server licenses are the number of databases. 5 for standard 100 for enterprise (50 for 2013 enterprise). For Edge/CAS/HUB roles (if separate) you only need standard.
Hope that helps.