What is so complicated about it? From what I understand, a laser (de)ionizes a big drum to put the image on it. The (de)ionized roller either picks up or doesn’t pick up toner. The toner deposits on the paper in exactly the same pattern it was picked up. A hot roller then fuses it on. If open source machines can 3d print with plastic and resin and UV light and high temperatures accurately enough to create physical objects, I don’t see why it should be any fundamental trouble to have some system capable of moving a laser across a 2d plane/roller with either optics or mechanically, and aside from whatever material they use on that image drum, all the parts are just simple rollers and heaters and high voltage, which are essentially jellybean parts at this point, even toner cartridges and rollers are essentially commodity items. Optics would be better if you want it fast and accurate, I suppose, but there’s no particularly complex magic and nothing top-secret that would be difficult to develop as far as I know. An open source one will probably be slow and clunky and maybe imprecise and power-hungry, but speed and efficiency and precision are not magic and are not fundamentally required for the principles of operation, it’s something you can improve over time.