This is a work in progress.
Our goal is to be able to read and write the contents of GM Powertrain Control Modules, such as the 12200411.
Reading is working well. Writing is working well enough to try it on your project car, but you probably shouldn't try that with your daily driver until it has proven itself a little more.
https://github.com/LegacyNsfw/PcmHacks/wiki (The wiki)
https://pcmhacking.net/forums/viewforum.php?f=42 (The GM section of pcmhacking.net)
http://pcmhammer.org (a shortcut to this GitHub page)