There seems to be a lot of confusion regarding CALs, for any Windows service you need a CAL unless it's explicitly excluded, yes, a CAL is needed for DHCP, a CAL is needed for DNS a CAL is needed for nearly anything.
From my understanding if MS thinks you are breaking CAL requirements, they will ask to audit which most places will refuse, after this they will purse more aggressive legal means.
Source: r/sysadmin · by /u/nwmcsween