The author of SoulFu now provides the source with the installer. Download the latest version (Windows only) and install it and there is the source code contained in the installation. That gives me hope of a future version of the game for Linux. :-)
The license is a little funny though - it is not a standard open source license and basically forbids a few things that you should read about if you are interested in modifying the source.
There's an interesting article on "What makes a good Civ game" (pages 1 2 3 4). Most of it is just common sense but it would be interesting to analyse what parts of it are applicable to FreeCiv. The article is nothing new (circa 2003) but I enjoyed reading it anyway.
I've been searching for more information on a 3D version of Exult. It exists, but in terms of the source and/or a relevant project page (with something more than a description). The only decent information I can find is in a 2 year old locked forum thread, which is a shame because it looks like a really interesting addition to the Exult scene and could attract a whole new generation of players. Sadly now it seems inactive.
There are many game ideas that never get realised, but given the hobbyist nature of open source [i.e. not bottom line driven] we are blessed with a blank canvas from which to start with and you can paint it however you like.
I would love to see a game inspired by Castles. In this old classic you got to build up a castle, selecting the height of the walls, and periodically you would get attacked by invading forces so you would place your defenders and watch the battle unfold. The end goal, of course, was to prevent your castle being conquered. For those with a good memory, this is the second time I've mentioned it.
So, what other games are missing from the scene? What ideas - new or old - are realistic enough to be tackled yet original enough to stand out? Comment here or in the forums with any ideas. :-)