CALs aren't monitored by SQL Server, but if you get audited...
25 CALs means you have max 25 people accessing that server. If you have more than that, and you get audited, you'll probably end up paying huge fines.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability