Whatever the proprietary Neanderthals may think, it's becoming clearer by the day that open source is, or will become, the natural state of software. "Nature" exerted her will yet again with the announcement that Electronic Art's SimCity has been released as open source under the GPLv3 license. The game was written back in 1983 (actually, before then) and so much of the code is too old to be useful except for research purposes.
But there's a lot of value in that, as Bill Simser notes:
There's still a lot of craptastic code in there, but the heart of the software (the simulator) hasn't changed. I know there will be efforts underway to port it to a better platform, replace the age old graphics with new ones, rewrite the graphic routines with modern-day counterparts, etc. The modern challenge for game programming is to deconstruct games like SimCity into reusable components for making other games! The code hopefully serves as a good example of how to use SWIG to integrate C++ classes into Python and Cairo, in a portable cross platform way that works on Linux and Windows.
It's like starting over from a familiar core, rebuilding the game into entirely new possibilities. On days like this I wish that I could code....