Google Glass, being succeeded by Project Aura, was an ambitious project with a lot of potential to go in a lot of different directions. Unable to find a cohesive vision that would justify the work involved and the device's high price tag, Google eventually gave up on Glass and scrapped their Glass Explorer project to sell only to enterprise customers. With a project as full of possibility as Glass, of course, this was not the end. People continued using and messing around with their old Explorer edition units to see just what Glass was capable of. One Glass owner, Reddit user jtxdriggers, decided to take messing about with Glass to its logical extreme and threw a build of Android 4.4 KitKat on the wearable, custom built from the Android Open Source Project repository and the device tree used for Marshmallow on devices running OMAP4 processors like the one in Glass.
He posted a picture of the newly built software running on his Glass set, showing the custom kernel version and build number in the settings menu. All of the code was compiled by hand from the codebases by cobbling together the closest or most fitting pieces for each part of the project, leaving a bit to be desired in the way of bugs and usability. jtxdriggers reports the interface is a bit janky and the touchpad on the Glass headset acts like the touch screen, making it difficult to do much except pull down the notification shade. At present, he's interacting with the device via the Android Debug Bridge on a tethered PC. One user, justarandomgeek, suggested trying out a bluetooth keyboard, but jtxdriggers has been unable to test such functionality at this time. He did note that it should work, in theory, since he's using the same code blobs that a project like SlimRom or Cyanogenmod would use to hook a KitKat Android phone to a keyboard.
Although the practicality of the project is limited by Glass' interface and the way the drivers interact with stock Android, jxtdriggers has stated that this project opens up a world of new possibilities for Glass. At this point, anybody who can develop a normal Android app can develop for Glass or even port existing open-source apps over, given some interface and display tweaks. jxtdriggers has not released the source code at this time, but says he's considering putting up on GitHub once he's more comfortable with the way everything functions and he's squashed some of the bugs.