To add to what's already been said... Nothing is "projected" in the sense that that word usually conjures up. There's a big curved mirror, and it reflects the image of the monitor. Because the image is mostly bright objects on a black background, you only see those parts and due to the curved mirror they appear to "float" above the screen area where you are looking. It's an optical illusion. No fancy holography here. You can see this effect demonstrated at most science museums.
Holography is a much overused term. Its been associated with just about every 3D technology primarily due to the fact that people recognize and can draw a parallel with the concept.
A "Real-Image Display" is the proper name for this system. It is almost certainly a spherical, rather than a parabolic mirror and it does indeed "project" light. If you take a piece of translucent material and place it where the images are, you will see them come to focus on the material at the exact point where your brain tells you they are. You think that they exist there because the light being projected from the system strikes the receptors in your eyeballs at the same angle and position as light reflecting off of or being generated by a real object in that location.
The reason the on-screen objects appear to be on the surface of the table is that the optic actually collects the light and brings it to focus at that point. It's still a 2D image, but it appears to be pasted on a plane in 3D space. And, as you stated, black is the absence of light, so it can't be projected. Therefore it disappears.
You may have seen me write that I have my name on a few patents through the "day job". Coincidentally, they revolve around this type of technology

RandyT