Interesting development, but readers must not be mislead by "fuel-free", as if it may be free energy. It simply means that as far as could be detected, it does not "throw out" a reaction mass, but it still needs a constant supply of electricity. In fact, the test item produced barely more than a mN worth of thrust for a kW of electricity input. It is about a thousandth's of the weight of an apple on Earth, while consuming the energy of a medium microwave oven.
If it holds up under further tests, the main thing is that it is more efficient than any present form of electrical propulsion, where ions are thrown out at the rear, being accelerated by electricity-driven magnetic fields. Here there is apparently nothing, not even photons, thrown out at the back. This violates a few laws of physics as we understand them, including the conservation of momentum and Newton's Third Law. But, who knows?
The leaked NASA report is here
The peer-review was just on the test itself, not on the physics of the device.