Mark's stuff sounds like the same old perpetual motion machine hoax. Basically anything using the name "free energy" is a hoax. Technically solar cells and such are "free energy" but the term's almost exclusively used by the quack/faker field.
Faked videos of demos are REAL common. Get used to it.
Joe cell's an old, old quack job. It can make hydrogen at the same rate as any electrolysis cell. It's useless for increasing mpg (much less eliminating fuel!) because not only can you never get out more energy than you started with, an engine wastes about 80% of the fuel's energy as heat, then the alternator making DC and the cell making H2 could be 50% efficient at best (actually you're gonna be quite a bit less). The things about making "Brown's Gas" as a special, super-secret completely unknown form of hydrogen are also bogus.