Just skimming the Wikipedia article, no. I don’t believe there’s any claim that they could be used as a free-energy machine, either. There’s a different between free propellant and free energy.
You’ve heard of the quantum foam, right? The basic gist of the quantum foam is that fluctuations in the vacuum energy of empty space cause the spontaneous production of matter/anti-matter pairs (usually electron/positron pairs, but there’s no reason higher mass particle pairs can’t be produced given higher fluctuations). These particle pairs a) pop into existence, b) live for a few small fractions of a second, and then c) collide, paying back their mass energy to the vacuum.
It’s possible to interrupt this chain of events at point b) by separating the two particles, thus preventing annihilation. The thing of it, though, is that the vacuum energy must be repaid from somewhere. If it’s not going to get it back from the particle’s mass-energy, it has to come from something else.
This is the mechanism that underlies Hawking’s classical theory of black hole evaporation. The particle/antiparticle pair are created just above the black hole’s event horizon. One of the particles (particle A) are created flying in the direction of the event horizon. By conservation of momentum, the other particle (particle B) is created flying in the opposite direction. If Particle A crosses the event horizon, and Particle B is created with enough momentum to escape the black hole, that mass energy is lost to the vacuum. It needs to be repaid from somewhere, though, and it’s repaid by the black hole. In spite of the fact that the black hole has just absorbed a massive particle, the black hole actually loses mass.
In the quantum vacuum thruster, the matter/antimatter pair are separated by a strong electric or magnetic field. That field, which is generated by the ship, needs to contain a huge amount of energy. When the particles are separated, it’s the electric/magnetic field that repays the energy to the vacuum. The electric/magnetic field is also used to accelerate the newly captured particle pair away from the ship, generating thrust.
So, the ship still needs to be able to generate a huge amount of energy. Significantly more, in fact, than would be required if they carried propellant along with them. But they’d get away without having to carry the mass of that propellant, and without running the risk of running out of propellant.
The whole concept, basically, is built on the idea that we’ll overcome the energy production side of things.