Unless you're the C2/SOT, you wouldn't be able to possess the machinegun after your 'friend' registered it. In addition to joe sixgun not being able to register new machineguns after 5/19/86, machinegunes registered after that time are restricted to law enforcement/gov't/military and export only.
The "Lightning Link" is also known by its formal name as the SWD AR-15 Auto Connector. It's a drop-in machinegun conversion that works with all semi-auto fire control parts. There are something like a thousand that were registered before 1986.
An AOW is "any other weapon" which is the NFA classification for guns that don't fit into other categories (like machineguns or short-barrel rifles). AOW includes gadget guns, smoothbore shotgun pistols, and also pistol-type firearms with two handgrips and no stock. Since an AOW isn't a rifle, pistol or shotgun, legally, it's not subject to the 94 AW ban. It can have any of the pre-ban features except a shoulder stock (collapsing or fixed).