PMEquator is also released as Freeware-openSource (its a educational game)
And possible soon Stris will be released too as OpenSource.
One thing that Im trying to do with the OS2world Gaming site is contacting teh authors of old (and unsupported) OS/2 games and tell them to make them freeware and if they can release the games as OpenSource so other developers can learn from it. For the moment I had luck with this games.
I hope to get more games soon to be released as freeware-OpenSource.