As far as I know Mark G. and crew are using old Z-Corp machines to print refractory plaster molds. The rest of the process is a traditional glass technique sometimes referred to as Pate De Verre. You should understand that these 3dp molds suffer the same restrictions as most any casting molds. And no matter how the mold is made, the furnace set up and finishing work for this glass technique is still very time consuming. So while it's a very cool idea, the fact remains that If you have a few hand skills and an electric kiln ANY of those designs could be done just as easily the old fashioned way. You just wouldn't have to get your hands as dirty.
-G "Where the spirit does not work with the hand, there is no art."
Leonardo da Vinci