CryEngine recently moved to a pay what you want price structure with the release of CryEngine 5. Then with the release of CryEngine 5.1 a few weeks back, they had this to say:
Git is a very widely used version control system that allows users to instantaneously access any revision of a file that has ever existed in their repository. This makes comparing revisions of a file and tracking changes over time very convenient, particularly as each time a set of changes is committed to the repository, a description of the change can be added. EDIT: We are finishing up the last details and users will get access to Git very soon.
Well that “very soon” is today. The CryEngine source code is now available on Github. The console (Xbox1/PS4) specific bits still require a proof of appropriate license to access, but otherwise everything is here.
Keep in mind though, this isn’t a typical open source release and is governed by a proprietary license. Read well before using!