Hey Chuck. You can request the SDK from Canon here.
You have to fill out their form requesting access to their SDK. I had to supply them with the S/N of my XL2 before they would even get back to me on it. That was about a month ago. I am still waiting for the approval and download instructions... Not the fastest of processes.
Let me know if you end up hearing back from them quicker than I. The only dissappointment that I have right now is that they only support VB6. I was hoping that with a flash update, they would start supporting .NET.