The Gottlieb IP is apparently controlled by Gottlieb Development LLC, not Steve Young/Pinball Resource. He is one of several licensees for Gottlieb products. He may ultimately sell newly approved products, but I don’t know his level of involvement in approving new products in conjunction with Gottlieb Development LLC.
Gottlieb Development LLC is willing to license more Gottlieb material. See here: https://mondialgroup.com/gottlieb.htm