Aquaria has gone open source under the GPL! Now all four of the games that pledged to open in the Humble Indie Bundle are officially open source — the others are Lugaru, Gish, and Penumbra Overture. I am especially excited about the modding possibilities for Aquaria because of its excellent level editing tools. Here’s a video showing an early version of the editor:

After the huge success of the Humble Indie Bundle, and the raise of over 1 Million Dollars in donations – the games in this “project” are “freeing their sources”.
After Lugaru and Penumbra Overture freed their sources, Gish is now following their example.
The source is under GPL and can be downloaded from here.

As of 5/11/10, Aquaria, Gish, Lugaru HD, and Penumbra Overture pledge to go open source.

Following the recent success of the Humble Indie Bundle, developer Cryptic Sea has released the source code for its 2D physics based Gish platform game

Lugaru HD was a part of the Humble Indie Bundle which allowed users to pay whatever the want for some great cross-platform games. They said they will open-source the games if they reach 1,000,000 - which they did, so all the games are about to be released as open source.

In the spirit of the Humble Indie Bundle, we have decided to release the source code to Lugaru! Our community has already made some great mods by editing the levels and graphics, but source code access will allow for much deeper modifications.

The games in this second Humble Indie Bundle include Braid, Cortex Command, Mechanarium, Osmos, and Revenge of the Titans. The game titles aren't too amazing, but they're all natively available for Linux, Windows, and Mac OS X.

Wolfiregames the developers of the Lugaru that are currently working on Overgrowth have posted about The Humble Indie Bundle – Pay What You Want Program! Five games in the price that you decide !

It has been in our minds for quite some time and now finally it has become reality: Penumbra:Overture and the HPL1 Engine are now open source!