This gives me serious scam vibes - cold fusion in a new spiffy jacket. Their 28 hour run is essentially running a Farnsworth fusor, BFHD.

I don't know anything about this new company, but muon-catalyzed fusion is legit. Because the muon is 200 times heavier than the electron it is much closer to the nucleus, and creates a better shielding effect. The question is what it takes to make muons in an energy efficient manner.

https://en.wikipedia.org/wiki/Muon-catalyzed_fusion