I'm a newbie to this whole 3d printer world but I've been interested in getting one. I've narrowed it down to an Ulitmaker or a makerbot 3d printer. Although I keep on hearing that the Ultimaker is open source and uses g code. I know that open source means that you would be able to see the original code created and be able to alter it but what does that have to do with 3d printing and how does it relate to G Code?