You can do it without "hacking" but it requires building your own harness adapters. Our Passat's original wiring is 100% intact - no changes to the stock harness whatsoever.
I was looking at a new Jetta on the road tonight, and I don't think that it is at all similar to the Passat's rear lighting. The Curt controller is required on the Passat because the body control module duty cycles single-filament lamps in order to create the different lighting functions. The Jetta TDI, on the other hand, controls its lights very differently... the brake lighting doesn't even go through the BCM at all... I'm not sure if the brake/park lights are single or dual filament.
Whatever it is, you can absolutely make the hybrid lights work if you have decent wiring skills and don't mind buying some factory repair wires and building your own adapter harnesses. It won't be cheap, but it will probably be less expensive than the kits. If you don't have the required wiring skills and tools, then an adapter kit is probably the best way to go and will save you a significant amount of time.
