Windows CALs are for either user or device server access. RDS CALs are for remote desktop application server access.
Some info here on windows CALS
https://www.microsoft.com/en-us/licensing/product-licensing/client-access-license
and RDS CALS here
Better to direct legal licensing questions to a trained microsoft licensing specialist or ask microsoft directly.
https://www.microsoft.com/Licensing/servicecenter/Help/Contact.aspx
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