1. Should I shoot the talent against a white backdrop or bluescreen?
Blue (or green) screen. It is easier to replace the green with white than to shoot on white and eliminate shadows.
2. Which program accepts HDV files and outputs GIF animations at these frame rates?
Premiere Pro will export animated GIF files (without audio) using Export Movie.
3. I assume perfect uniform ligting will be critcal in order to make to GIF background mesh with the webpage background?
Light the greenscreen correctlu and you should have a perfect white to work with.
4.Alternatively is it possible to have a flash video (with audio) that auto loads with the webpage and then loops? The video must match the webpage background and not appear in a flash (or other) video player though.
Yes. Many sites have such things. Usually advertising.
Steven
https://www.stevengotz.com