There is always something going on...
If you are interested in the source code, it's on GitHub. If you are having issues with the game, you can add a bug report to our bugtracker, and we will take a look at it! We have continuous integration using Travis CI. This allows for automatic checks that the code compiles on every push and pull request.
Finally, if you are interested in modding, check out the modding docs, they document all of the aspects of making changes to the game data files.
Currently there is only one guy doing it all - code, artwork, the lot. If anyone is interested in helping out, let me know.
I try to release every three weeks on the weekend.
The code is all C++. It compiles on Linux (GCC) and MSVC 2010 Express Edition. I haven't tested any other version of MSVC.
The artwork is all done in Blender (the originals are in the repository). I use the Gimp for textures.