I believe RSK is Rich Kulawiec. I have on my computer a copy of a message Kulawiec posted to the Usenet newsgroup rec.music.folk (and crossposted to some other newsgroups) in April, 1993, with the subject, The Annotated "American Pie". I haven't done a close comparison, but the "program notes" in the DT seem to be pretty much the same as that Usenet post. I suppose the Usenet post is available on Google Groups for anyone who wants to take a closer look.

One difference I spotted is that the Usenet post has some introductory material on how the annotations came about, and a long list of credits and a revision history at the end.