This engine has been around for a while, and as exciting as it looks, it's simply not practical to use. I don't know of a single game to have used this, and judging by their website they're currently targetting this at representing real world data captured using lidar (basically very high resolution radar using a laser), rather than games.
There are two major issues with using it for games. The first is that there are no good tools for creating models for use in the engine, all current tools (blender, 3dsmax, maya etc.) are for creating polygon models. To some extend Thrive could work round this, as most of our models will be procedural, but I have no idea how hard it would be to actually do this. The second problem is that the engine (to my knowledge) doesn't support animation, I've yet to see a video of anything other than a static model. Another possible problem is that unlimited detail requires unlimited memory, which we don't have (notice that many of their videos show the same model repeated infinite times), so I'm not sure how much detail we could get out of ~2gb of ram.
Finally, I suspect that even if we could use the engine, it's very unlikely to be free. Having said all that, given that we're likely to be using almost entirely procedural models, we may be in a fairly good position to use this in a game, so it may just be worth contacting them to see just how much it's cost us to use.