Is a ground station radio license required for UAS operations in the US?
Air -> Air, or Ground -> Air describes the ultimate path of the message. It doesn't describe what's being discussed. So:


  The communications would concern a sUAS in the air, but the radio is physically on the ground.


If the radio endpoints are both on the ground, then that's ground -> ground transmission. Put it another way - if a controller talks to a fireman over the radio, about an aircraft in the air, it doesn't magically become a Ground -> Air transmissions.

The definition matters primarily for technical and practical reasons (E.g.., Air -> Air radio will have a better range than Ground -> Ground because of nothing being in the way). If you're on the ground, you're a ground station - it's as simple as that.