it would be called HHO and not H20 if the molecule bonded together differently. If he used electrolysis to create it from water, then the H atoms have extra electrons, that's why it can do what it does. I bet its called HHO because the two Hydrogens are bonded, and then one of them is attached to the Oxygen.Either that, or it coud be that the extra electrons int he molecule cause it to stop being so polarized, and the Hydrogens drift away from the tetrahedral structural shape. So its not really water when its 'burning,' but as it reacts with whatever it burns, its gives away those electrons, and goes back to good old water again.
So basically you'd have the structure H----H(+)----O(-)? That isn't going to be stable for any significant length of time, it'll just rearrange back to water in a tiny fraction of a second.
If you're proposing just adding electrons to water, without breaking bonds to give the weird double bonded hydrogen, then the electron(s) will have to be added to the 3a1 antibonding molecular orbital, which is much higher in energy than the largely non-bonding 1b1 orbital that the highest energy electrons of water occupy. You could improve the situation slightly by compressing the bond angle to 90 degrees, but adding these electrons will still greatly weaken the H-O bonds. This simply isn't going to remain stable for any significant length of time (though yes it will release some energy when it drops back to the ground state of water). As I've said, water would not be acting as a fuel here, but a (very short term) energy store in any case.
There is absolutely nothing in this video clip which cannot be explained as follows:
He electrolyses water by the normal process to give a stoichiometric mixture of H2 gas and O2 in a 2:1 ratio. He then burns the two conventionally in a torch to give heat and water as a product. There's no need for any weird gases here, he's just making hydrogen by electrolysis and immediately burning it again (very inefficient energy wise I suspect). This gives neither a good fuel source or store.
My skepticism is increased by the ridiculous claims of a "slightly warm" flame that can melt metal. Heat is heat, whether you're burning H2, oil, coal, wood, diamond or weird made up substances. If it doesn't produce enough heat to burn you, it's not going to make much impression on brass. The nozzle not getting hot would be a feature of the nozzle design, not the fuel. Heat will conduct equally well, whatever its source.