Oolite

Oolite is an Elite-inspired open-source space trading and combat simulation, with context and story similar to the original Elite. There are many optional expansion packs called OXP:s that can add functionality or missions to the basic game, though new players are recommended to limit the additions so as not to make the game too difficult to play. Thus a few 'recommended' lists are presented on the games community forums.

The gameplay revolves around trading, buying commodities in one system cheap, transporting it to another system and selling it for profit. You travel between systems through wormholes in hyperspace, called 'witch-space', in which aliens may attack your ship. En route in normal space to the target system your ship may be also be attacked by pirates, so it's recommended to have some armaments to survive in the long run. Money can be earned by collecting bounty from destroying the pirates, or mining asteroids. Optionally you can become a pirate yourself and waylay AI trader pilots, but this gets you in trouble with the police force, and limits the available trading options. The game is open-ended and progress are kept track of by amount of money accumulated, and the player status, going from 'harmless' to 'elite' ranking.