The business model of this machine (well, aside from the advocacy/self-promotion angle others describe) is that one person buys this, then allows others to use it to finish their "80% receivers". (And then they do a hell of a lot more work to turn it into a safe, functioning gun, but that's assembly, not machining, a lot more people are good (enough) at the former than the latter.)
No it doesn't. Most people who have computers with DVD drives do not sell DVDs. On the other hand, most people who have gun manufacturing machines do trade in guns.
Just as relevant, you don't need a license for DVDs, but you do need a license for guns.