What they're obviously talking about is perceived recoil.
Physics tells us that in general, what they're saying is impossible. Recoil exists. But if it's harnessed in such a manner to make it negligible to the shooter, then the gun is, in effect, recoilless.
What I think they're doing is trying to harness the recoil pulse and redirect it completely, or substantially, into a rotational force. If what they are trying to do works, then perceived recoil, the thrust back when you fire a gun, would be channeled into something that we wouldn't perceive as traditional recoil.
This is already done with artillery. The arrestor mechanisms channel the recoil into cylinders containing pneumatics, or springs, or a combination of the two. Yes, the barrel still recoils, but the carriage can stay largely in the same place.