Many in the past have asked whether any of this would run on mainstream game engines. I could not see a reason why not. The VoxelFarm engine outputs traditional polygons, in theory it could be plugged into any engine using polygons for rendering, physics, etc. That remained a nice theory until recently. Now we have some hard proof:
This screnshot shows the VoxelFarm realtime engine providing polygons for terrain in Unity.
Here is are a video. It shows a simple physics test and a little bit of walking. The capture speed and resolution is not good, but hopefully you will get the idea.