I would speculate that Calumet views the market for this material as sufficiently small that it's not worth the trouble for them to package it for sale. I would agree with that. I'd also speculate that it annoys the heck out of them when someone else illegitimately profits from their copyright. As it should. Making this available material on a free archive is an excellent solution. It undercuts the ability for anyone to sell copies and earns Calumet some good will for something they're not making any use of.

Good luck!