This is an interesting project, which splits up 3D printer control between the micro-controller and a separate computer (such as a Raspberry Pi), but not in the way OctoPrint does. The computer is used to calculate and schedule all the movement, whereas the micro-controller simply executes the work at the appropriate time. It can even handle multiple micro-controllers and keep them in sync, in case e.g. you want one controller per axis! Keeping the micro-controller codebase small supposedly helps maintain higher precision movement and a larger step throughput, and makes it much easier to tweak things, because now you're just changing a configuration file on a Linux machine, rather than recompiling and flashing new micro-controller code. Here's the feature list, where the author explains the advantages a lot better than I do. Definitely one to watch!