The rep rap Helios has two actuated joints on the arm, the "shoulder" and "elbow". So the arm itself provides all your reach in X and Y, then the end effector moves in Z.

The sculpto has one joint on the arm that swings in and out, and then the bed itself also rotates. This gives you your X and Y. The arm then moves in Z. "Bipolar" seems to be a marketing term for saying both the arm and the bed move in a polar coordinate system.

So mechanically, it's a bit different from the helios which is a SCARA with a shoulder and elbow, the sclupto has an elbow and then the bed spins to give you access to the rest of your print volume.