Aw that sucks. It did seem too big for him to complete. After minecraft it seemed like he wanted to do an equally big and ground breaking game that could top its success, and why not? He had all the money and time in the world to do it but that's a recipe for disaster. Hopefully the fan effort can translate the basic concepts into a fun game.
The core of the game was the programmable computer idea. You can program the computer to do whatever in your spaceship. Make a clock, code and play original games, setup your own security system for accessing the computer etc. Whatever a real computer could do. The computer works in conjunction with all of the on board spaceship electronics so you can control the thrusters, air supply, guns, communication etc. With these tools you go around the universe to scavenge more parts to upgrade your ship and computer so you can do more. While adventuring there are other human players doing the exact same thing, so you can fight to see who's setup is better, hack/get hacked, or maybe work together, trade, whatever. This is fucking ambitious and I'd love to play it someday.
Hopefully more developers are inspired by this stylized low poly low res texture look. It looks great.
And good luck to Notch in whatever he does next.