Development on Greenbelt stopped about six months ago. I personally have just started to learn some Visual Basic, and I'm going to try to remake Greenbelt in VB. Mapboy is currently working on some other, somewhat more secret projects in the Unity engine, so I'll mostly be working on this on my own. I'll see how far this gets. The problem with Visual Basic is that it uses .Net framework and will not run on Mac. I'm uncertain as to whether it'll run on Linux or not, but mac-users won't be able to play Greenbelt if I remake it in Visual Basic. I'll release the Visual Basic version it if it gets to a point where it is about as far along as the current Java version is.
Visual Basic remake