It looks like one of those ladder mechanisms, modified. Contractors routinely put big extension ladders up on their high roofs. There's a crank system to raise and lower the ladder rack down over the side of the van for personnel access.
Personally I gave up on the idea of carrying a rigid kayak on our van. I think one would have to be really serious about kayaking to go to all that trouble and then what happens to the van's aerodynamic stability with a contraption like that? I haven't seen a single example of any device on the market that really inspired my confidence, whether roof-mounted or rear-mounted. Rear-mounted of course opens up the additional possibility of theft.
For the less serious, there's plenty of tame fun that can be had in inshore quieter-water environments with an inflatable kayak, rather than a rigid model. This past weekend, I finally got around to sewing a custom roof carrier for ours. It fits neatly under the leading edge of our solar panels. Blog post with instructions
here, and here's a pic of the finished product: