this is not even technically a game. he's just building an engine for one as far as I can tell...
It is more of a game than a lot of the junk put forward on Steam these days. I have played more hours of SE than any of my other games. I think right now would be a good time to get a SE concept page going on Greenlight to see how the community responds to it. It may be a planetarium software but Steam also supports software, early access games, and Free to play. If SE were put on steam this would also grant Steamworks tools allowing the program to be expanded and giving him a much larger audience base for future games. Plus imagine how great SE would be if it had workshop support and the Steam servers for updates, community pages, and sharing mods.