As many here may remember that this whole deal started with Ares Arms in Oceanside, CA by selling people 80% AR lowers and letting them push the button on their CNC machine to circumvent having a manufacturers license.
As for the ATF Letter posted in the link above, nowhere does it state that people may not loan each other tools to create a firearm. It says that a business (including an association or society) or any person (including any corporation or other legal entity) engaged in the business of performing machining, molding, casting, forging, printing (additive manufacturing) or other manufacturing process may not let people use their equipment.
I think this means that @IronMonster probably would go to jail for letting us use his shop and/or equipment, but if a group of people met in someones garage that wasn't "in the business" and had a build party and loaned each other tools, they would be OK.
As I'm not a lawyer or scholor please correct me if I missed something in this letter that proves that I'm wrong.
Ray
PS, if there is going to be a build party (especially for newbies) please wait or schedule another one in/or after mid June, so I can attend.
If one happens, I suspect there will be more