FreeCiv: Classic Strategy

Freeciv is a single and multiplayer turn-based strategy game for workstations and personal computers inspired by the commercial proprietary Sid Meier's Civilization series. The game's default settings are closest to Civilization II, in both gameplay and graphics (including the units and the isometric grid).
Released under the GNU General Public License, Freeciv is free and open source software.

Players take the role of tribal leaders in 4000 B.C. who must guide their peoples through the centuries. Over time, new technologies are discovered, which allow the construction of new city buildings and the deployment of new units. Players can wage war on one another or form diplomatic relationships.
The game ends when one civilization has eradicated all others or accomplished the goal of space colonization, or at a given deadline. If more than one civilization remains at the deadline, the player with the highest score wins. Points are awarded for the size of a civilization, its wealth, and cultural and scientific advances.

FreeCIV

The original project can be found at sourceforge and further instructions here

AROS port was handled by Bszilárd Biró, and it has still some quirks but it's regarded as functional.

Download AROS FreeCIV at his Web page.

AROS FreeCIV running on a window