This doesn't really have anything to do decompilation, but I figured readers here would be interested to know that the source code to Will Wright's SimCity has been released. Don Hopkins is the man responsible, his original mission to get SimCity running on the OLPC (one laptop per child) computer. For legal reasons the code has been released under the name "Micropolis". Much of the source has been ported or transcoded to C++ from C, with portions moving to Python and Swig with a TCL/Tk interface. It can be built for Unix or Windows and binaries are available.
SimCity is notable for being one of the only games, and certainly the first back in the C64 days, to make heavy use of cellular automata. Being CA junky I had to take a look, and although I haven't delved too deeply into the source code, I likes what I sees. Fun stuff, makes me want to fire up SimCity for one more go.