Yes, the top and bottom can move independently. We are using two windows motors: one driving the top and the other driving the bottom. The window motor that drives the bottom is hidden from view. Go
here for the latest episode of American Robot to see it in action.
The tubes are just regular 'ol PVC you can buy at any hardware. They're great to prototype with. The pulleys I believe are from McMaster, but I don't know the part number (Rob could answer that).