Star Shipping which I wrote about now has a GNU/Linux client which you can buy from the official website or via The Ubuntu Software Center.
Gameplay Video
About
In Star shipping Inc. you take the role of the captain of of a cargo ship traveling between star systems to trade goods and commodities in strive to become the richest star ship captain in the galaxy.
Star shipping features high resolution beautiful space backdrops, planets, aliens, nebulae, space ships, items, and characters. The game includes an in game store where you can buy upgrades to your ship in order to increase performance and get a higher score. For example, you can buy upgrades to get more speed, strength, or resilience. The game also features a bank where you can keep your savings and where you can loan cash in times of need.