Cub Linux (formerly Chromixium) is an Ubuntu Linux distribution focused on the open source browser Chromium to provide an operating environment much like Chromebooks. What that means is that after making a bootable USB drive, you can wipe out a laptop and make it act like a Chromebook.
Notice that I say it “acts” like a Chromebook, it doesn’t turn it into a Chromebook like Neverware’s Cloudready product. There isn’t a management piece, and you’ll have to manage the users manually. You do have access to all of the Ubuntu applications that are available.
Use cases for Cub Linux could be those classrooms where students aren’t quite logging into the computer yet, such as kindergarten or first grade, or if you have older equipment that you would like to put into service. Cub Linux could be used for machines that need to do a little bit more than what Chromebooks can do, such as video editing with OpenShot or audio editing with Audacity.