Some kind of version control would probably be best in this situation. When you have an open source project and multiple developers interested in working on it, version control is the only way to go.
If you checked out that archive I linked to, the way it is set up there would allow all of the old code to stay in place, but we could selectively move things to other files. Really all you would have to do at that point is copy the body of the function from game.cpp to another file (like building.cpp or loot.cpp, some name so we can group like things together). I am sure that you have some functions you modified while I made those split up files. All you will need to do is copy your new functions over those old ones, in whatever file they are in.
I started changing some ints to unsigned ints to get rid of those warnings, but there are far too many, so people using GCC will need to just deal with it for now. I also think I accidentally changed one of those ints to unsigned int which caused the voting thing to skip to the end when a button is pressed (this actually works nice, but I think we need an actual button to do this, and we need to change that int back as I don't know what other things this changed), and also disbanding seems to immediately close the game.
It would probably be best for you to get a Subversion or CVS server set up. It would probably be a great idea to register the project on sourceforge.net. They will give you a free SVN and/or CVS server, a web page with 100MB of space, a nice release system for releases, and bug/request trackers. I think you should register the project on SourceForge, and then let other interested developers join the project. (You should upload your code, not the code I made. I can just split it up again and get the changes to unsigned int right this time.)
[ June 11, 2007: Message edited by: Grundee ]