The G-code interpreter running on the Arduino is currently the one from Contraptor.org.
I generate gcode in Grasshopper for Rhino, stream it to a file, and send the Gcode with gRemote made in processing, this creates a nice and fast workflow for testing and printing.
As of now the printer is printing quite nice, but the paper feeder still needs some work in order for it to work more than ~4 out of 5 times. The paper main rod in the paper feeder is from an old printer, and I would like to figure out a solution to coat a steel rod, or maybe use O-ring to archive the friction required in order to move the paper. (Not everybody got old printers lying around) =)
As you can see from the pictures, I have tested quite a lot of different solutions. Let me know if you want to know more.