KerbalEdu requires an Internet connection when the game is launched for the first time. After the initial activation is done the online connection is no longer required. Other license games can be played with no Internet connection. The connection is, however, required if you wish to see the learning analytics for the gameplay.
With subscription to TeacherGaming Desk the internet connection is required, because logging in to TeacherGaming App and using Desk for running lessons and seeing learning analytics requires internet connection.