The CryENGINE powers Crysis as well as other games like Homefront 2, Monster Hunter Online, Ryse, and Warface.
CryENGINE is currently up to its third major revision and originally supported only Microsoft Windows but since then support has come to the consoles (Xbox 360, Wii U, PlayStation 3) along with mobile platforms like Android and iOS. One year ago I also revealed there is already a native Linux port of CryEngine 3 but that it was unreleased.
That news came from a source, who I will now say ended up being one of the people that I had ultimately referred to Valve as a recruit to work on their Linux gaming efforts. Anyhow, Crytek now has published a job posting that they're looking for a Linux programmer to maintain their Linux support for CryEngine.
The job posting at Crytek.com is simply for a "Linux programmer" in their Frankfurt office. The description reads, "The CryENGINE team is looking for a Programmer to work on the Linux version of the 3d engine." The first responsibility is to "Maintain Linux support for CryENGINE." Thus with the mention of "maintain", it appears the Linux port of CryENGINE already exists, as I had said one year ago. As time will show, it's for the client-side and not only the server port of the Crytek game engine.
Other responsibilities of the Linux programmer include maintaining and improving low-level engine systems, ensuring reliability of Unix-based build systems for SDK releases and special projects, provide support and training, and more.