I would have a very hard time releasing an open sourced game project. Modern gaming communities are shrinking every day because of the sheer volume of available titles. To risk further fracturing of your small player base by making your code open source (and spinning off dozens of "minimods") is an unpleasant thought. Most people who create mods dervive their prime source of satisfaction from seeing others playing their game the way they envisioned it. Letting someone else hack apart their code and release crazy versions (even if popular) is a hard pill to swallow.
