A couple of months ago Crytek switched CryENGINE to a pay-what-you-want model and now the game developer goes a step further by making the source code publicly available on GitHub.
On the company blog, Crytek this makes comparing revisions of a file and tracking changes over time much easier. Do keep in mind that the code is released under a limited license agreement, which carries some restrictions such as not being allowed to use the code for anything that is not considered gaming (like gambling, simulations, military and scientific projects, etc).
In the past, public CRYENGINE releases came with source code in a zip file included in the build. While this allowed users to customize systems as they saw fit, it was a simple drop of files. To see the difference in a set of files between one release and the next, both archives needed to be extracted and compared. Git makes this a lot easier, and since Git is decentralized, it can also be used just as effectively with no network connection. Further than this, however, it will be much more convenient for users to keep up-to-date with new CRYENGINE releases, as merging code branches is an area where Git excels. This has been on our internal roadmap for some time, but we wanted to take our time and make sure we got it right: once a file is pushed to a Git repository, it becomes part of the history and cannot be removed by subsequent updates (in contrast to other version control systems, which may allow changes and file revisions to be obliterated).