Aye, but it doesn't operate the trigger mechanism of a semi-automatic firearm for the purpose of causing the firearm to discharge cartridges in rapid succession. It lets you fire multiple guns, the shots are not successively from a firearm. It is just a legal as a 30 round ruger 10/22 mag.
Yeah, I think by the literal letter of the law, this arrangement isn't technically illegal. I figure each rifle is only fired as fast as one could do with a finger, the fact there is 6 of them is what makes it "rapid fire". Pretty sure the powers that be would choose to interpret the law differently though.