Hello Chuck Morris,
In my assessment, given that the third server includes services such as a file server and programs, it is necessary to have the RDS CAL. RDS Cal as addictive Cal is required for every user or device accessing advanced functionality. The number of licenses you need will depend on the number of users who will be accessing the server through RDS.
Here are two screenshots regarding the base CAL and addictive CAL; I hope they may be of assistance.
I recommend reviewing our licensing documentation: https://www.microsoft.com/licensing/docs/view/Windows-Server
Note: For licensing inquiries, we recommend consulting with certified Microsoft licensing specialists or your vendor. Licenses constitute legal agreements between you and Microsoft. As tech support, our expertise lies in addressing technical issues, and we can offer only fundamental information about CAL.
Windows Remote Desktop Server CAL 2022 (microsoft.com)
Regards,
Karlie