I spoke with Jerry Sussman tonight and described this video. He hadn't seen it, but told the story of how Julie Sussman had visited a library at Harvard and, under the supervision of an armed guard, made photocopies of the page with the two alchemists from an old manuscript. He confirmed that that formed the basis of the cover, as suggested in the video. I asked him about other claims, e.g. that the two alchemists represented him and Hal, that the caliper represented the REPL, that the correspondence between the second letters of the names was deliberate, etc. He was surprised by all of them.