Hello there! 
A game called Offworld Trading Company is free to own forever, as long as you claim your copy before the 22nd July.
Game Description:
Mars has been colonized. Now, Earth’s greatest corporate titans have been invited to build companies to support it. The competition to dominate the market is fierce in this fast-paced economic RTS from Civilization IV lead Designer, Soren Johnson.
With space travel becoming a reality and the easy-to-reach resources on Earth dwindling, hopeful people seeking their fortune are rushing to the next great frontier: Mars.
(Note that this game has been given free before. If you actively follow this forum section you may already own this game from a previous giveaway).
Enjoy!