The true sequel to Civilization, Sid Meier's Alpha Centauri continues the story of the first colony ship sent from Earth. Choose one of seven factions to play, and struggle for control
against the other factions, with or without Planet's help.

An expansion called Alien Crossfire was released for Alpha Centauri, which offers another seven factions to play as, more technologies, units, etc.

Although SMAC was ported to Linux by Loki Games in 2000, that port is very difficult to find and is no longer maintained.