How compatible is Freeciv with the commercial Civilization games? Edit
Freeciv was created as a multiplayer version of Civilization™ with players moving simultaneously. Rules and elements of Civilization II, and features required for single-player use, such as AI players, were added later. It is still a stated goal to let Freeciv's game engine be 100% compatible with Civilization™ I and II, but only as an option.
This is why Freeciv comes with three game configurations (rulesets): the civ1 and civ2 modpacks implement game rules, elements, and features that bring them as close as possible to Civilization I and Civilization II respectively, while the classic ruleset tries to reflect the most popular settings among Freeciv players. Unimplemented Civilization I and II features are mainly those that would have little or no benefit in multiplayer mode, and nobody is working on closing this gap.
Little or no work is being done on implementing features from other similar games, such as SMAC, CTP or Civilization III.