These tools are a work in progress. They currently support reading, writing, and data logging with General Motors P01 and P59 Powertrain Control Modules (PCMs).
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.
The most recent release will be at the top of that page.
Click "Assets" (below the description of the release) and download the .zip file.
Extract the contents of the zip file, and run PcmHammer.exe or PcmLogger.exe.