This is the CFS3 Terrain SDK. It contains the make_gsl.bat, MOSEditor.exe, and other useful items.
For [Microsoft Combat Flight Simulator 3] © Microsoft Corporation. [Terrain SDK] was created under Microsoft's "Game Content Usage Rules" using assets from [Microsoft Combat Flight Simulator 3]. It is not endorsed by Microsoft and does not reflect the views or opinions of Microsoft or anyone officially involved in producing or managing [Microsoft Combat Flight Simulator 3]. As such, it does not contribute to the official narrative of the fictional universe, if applicable.
By Microsof