The Humble Indie Bundle (pay what you want for five awesome indie games): "Now it's our turn to give back. As of 5/11/10, Aquaria, Gish, Lugaru HD, and Penumbra Overture pledge to go open source. We are preparing the sources right now and will be releasing them ASAP. We spent last night preparing Lugaru and it is available now. The code is still a little rough (no Visual Studio project yet, for instance) but hopefully with the help of the community we can rapidly make it more accessible to everyone.
Note, the games will be 'free as in 'free speech', not as in 'free beer'': see each license for the full, finalized details as they come out very hopefully this week -- stay tuned. It is the underlying code that will be made available to everyone."