Opensource

Actually kind of a necessity.

With an inkjet, most of the 'difficult' engineering and manufacturing is in the print head. The rest is just a basic x/y bot to move the head and paper around- easy engineering and manufacturing. They use someone else's print head so they get around all that. That makes this a fairly easy design- just figure out how to trigger the cartridge nozzles when the head is in the right spot, write some code for rasterizing the image into print strips, and you're done.

With a laser, there's a lot more work. You need an entire optical system (laser, spinning mirror, etc), you need high voltage stuff to charge the drum, you need a high wattage heating coil for the fuser, etc. There's a lot more engineering and coding work involved and more manufacturing also.