It is perfectly legal to allow friends, family, and customers access to your CNC machine for a fee. In many places you can find “build parties” where you get a kit for an AK-47 or ar15 type rifle that includes an 80% lower reciever plus tools and experts on hand to aid you in the final milling work and assembly. With this machine I imagine you could sell the 80% lower and the machine time. As long as the gun owners press the “start” button no laws have been broken.
Why not just go buy one? They aren’t that expensive.
Apparently they are more secretive than the Culper spy ring.