Is this plugin still alive? I was hoping to see this come together...

Yes, the project is still in development. The 3ds max editor is almost finished. But right now I am working on the release of my first (2D) game so I don't have much time right now to work on other projects. However I planned to get back to it - but that might take a while...

Have some new pictures of a somewhat bigger voxel terrain composed of multiple smaller terrains.
When you start out there is just one terrain sector but you can add new sectors in all directions. I am not really happy with this approach and what I will be doing next is that I will make it so that new sectors will automatically be created once the painting brush hits the boundary of the mesh.This way you can paint wherever you want to.

Also I will add some more brushes(ellipsoid/cube/cone/clone) and some special functionality like painting voxels onto the surface of other 3ds max meshes and 3D mesh to voxel conversion. I will update this thread as development continues so stay tuned