The original license (as of two years ago) only worked for one computer and activation. If you wanted to reinstall, you would have to email the creator of the game for another key, which he was happy and quick to provide. I believe the steam version just uses steam. I just messaged Shawn, the creator/programmer, for a steam key, and he gave me one since I bought the game about 2 years ago.
The game is small in memory size, but large in scope. As with DF, it's pretty incredible to have been programmed by one man.
You can command only various styles of small craft, civilian and combat versions. The focus of the game is on exploration with some trading and combat thrown in. Combat is really fun since it utilises newtonian physics, and will take some getting used to. You can get "officers" for your spaceship, and they confer various bonuses to your ship. You can have a carrier to support your small craft and buy/build stations. This is really fun in multiplayer, as people will take over different sectors of space.
Overall, I'd say it's a great buy for $7, if you're into games like Elite and Freelancer.
EDIT: One of the biggest draws for the game, is that anywhere you see, you can go. No loading screens. If you want you could land on a planet... you could use all your fuel to speed up and then coast forever until you crash into something because you can't slow down with no fuel, you can initiate your warp drive in the atmosphere and become a flaming wreck. There's also rumours of a hidden Earth somewhere in quadrants far away...