The Orbbec Body Tracking library (included with Astra SDK) is free to use until March 31, 2019. Please plan to update to a newer version before that date or contact firstname.lastname@example.org about license extensions and information.
The SDK times out every few months. When it does, the only notice seems to be in the Astra LOG file. Everything will seem to be working, but you will get nothing from the camera, as mentioned above. IOW, the "SkeletonRenderer" module will just stop generating events, and you will need to integrate a new SDK with a new time-out date built in.