I know this is an old thread, but here I am.

After watching the videos and picking apart the visible components, watching the slow mo of the blast, I can say pretty definitively that it's just a high pressure vortex launcher.

He probably compresses a fuel air mixture to high pressure, which is released all at once by a solenoid valve or something, that high pressure gas flows into a chamber with the correct geometry to create a high pressure vortex, which ignites as it passes the pilot light at the muzzle.

High pressure vortexes like that can travel a reasonable distance before puttering out, and as the gas only combusts after exiting the barrel unlike other combustion based vortex cannons it's still capable of deflagrating as it moves toward the target.

Cool idea, and I'm definitely going to try making one.