I have read a lot about full auto (machine) guns, and if anything is done to modify the gun to fire more than one round, on a single pull of the trigger, that would put it under NFA. This trigger looks like it has something that would make it illegal, as the fire control lever has 3 positions, safe, single, and 3rd mode. Since the trigger has "no take-up" and "no over-travel", they are going to try to convince the BATF that it does not come under NFA, as it is a normal AR type trigger. The issue is the extra lever control from single fire to 3rd mode.
This trigger system is not full auto, as there is no auto sear, which drops the hammer as the bolt locks. Their advertising states that the "third mode" has "positive reset characteristic", but if anything, other than an actual trigger pull causes the hammer to drop, it would be illegal. I would think it was designed so light that the forward impact of the bolt closing would cause the lightly held reset bar to release, causing the hammer to drop, while the trigger is still held rearward. Or it could be that this trigger is so light that under the 3rd mode, that the hammer may not always lock back, but could follow the carrier forward, as it closes.The hammer falling with the carrier closing may or may not cause a full auto scenario. If the ammo has light ignition primers, the pressure of the hammer following the carrier may have enough energy to hit the firing pin hard enough to ignite the primer. But the more likely scenario is it would not fire and you end up with a failure to fire. However the danger is it does work, and the cartridge fires before the bolt is locked or even fully seated, which is a serious issue. I doubt this trigger will be approved by BATF, unless large amounts of money changes hands. I can see how the Slide-Fire stocks were approved, as nothing about them has anything to do with the internal fire control parts.
I suggest to buy a slide-fire stock. They are legal, do not cause out of battery firings, and are relatively inexpensive, compared to the legal full auto gun prices. They are easy to move from gun to gun. I have one on my AR10, and it works great. If I keep pushing forward, it burns through a 20 round mag in two seconds. At the cost for 7.62/.308 ammo, I don't use it very often. I also had to put a compensator on it, to keep the barrel down and on target. The 7.62 cartridge produces twice the foot pounds of energy, than the 5.56 cartridge does, along with substantial more felt recoil.
Bob