My own personal theory (or at least the one I like to believe, based on zero evidence, lol): RiffTrax made it. They wanted to sell a riff of the Holiday Special because their other Star Wars riffs at the time were very popular, but it would have been hard to sell an audio-only HS riff unless there was an easy way for people to watch the special. So they uploaded it to Google Video themselves and added the crawl so the specific version they riffed was easily identifiable.
The only wrinkle in that theory to me is the timeline. The Google Video version was uploaded December 25, 2006, and Rifftrax released their mix on December 10, 2007.
going back through the thread more, there this post from Rikter in 2005, which mentions a DVD of the WMAR transfer. I would not be surprised if that was the origin point.