Solipskier), has just been released as an open source project under the MIT license. Curiously, it is the iOS version of the game that has been released, not the original Flash version.
Canabalt, if you haven't played it (play the Flash version now!), is a game all about collisions, and moving at incredibly fast speeds. Developers (or curious players) might be interested in Tuning Canabalt (part 1 & part 2), a series of blog posts about the fine-tuning of Canabalt's game mechanics. (The third part hasn't been published yet, incidentally.) The open-sourcing of Canabalt means that developers can finally take a look at the clever code behind the game.
Interestingly, this release, despite it being dressed up as Canabalt being open-sourced, seems to be more about the game library behind Canabalt: Flixel. Flixel is an open-source library for Flash game development, but it was ported to iOS for Canabalt. While there are no shortage of game engines and libraries for iOS, Flixel will make a great addition.
In other news, until the end of today, you can take advantage of the Indie iPhone Holiday Sale. Six great games are available for just $0.99, and 30% of revenue (after Apple's cut) will be given to the Child's Play charity. If you want to get your hands on a cheap copy of Canabalt, Solipskier, Drop7, Eliss, Osmos, or Spider, now's your chance -- over $30,000 has been raised for Child's Play so far!