The Apolyton Civilization Site is reporting on this forum thread which indicates that the source code to Civilization: Call To Power 2 may be released at some point in the relatively near future. The original Civilization: Call to Power was the first game published by the now-defunct Loki Games in May 1999 (see our Loki Timeline for more details). The sequel in question was only published for the Windows platform.
If this source release happens, it could enable the spread of this game to previously unsupported platforms, like Linux, MacOS X, and any of the BSD family.
Regardless, we will always have Freeciv.