One of the interesting things about games is that to the end user/player the majority of the value is the art and level design, two things which are extremely easy to divorce from the source (and thus license-able under whatever) so unless you're EPIC or somebody trying to specifically license tech open sourcing a game really doesn't make a lot of difference in the business model.

that said I'll add to the list DROD (one of the best puzzle series ever):

http://forum.caravelgames.com/site/SourceCode