Sorry Birdoasis, I missed your question there. Long day. Please take what follows as vague recollection, not definitive history.

Chemo is Bobby Easland, who wrote an SEO mod for OsCommerce a while back. This was/became Ultimate SEO URL's for OsC, and Chemo is generally acknowledged to know a little bit on the subject.
Someone possibly Dreamscape? ported this to Zen Cart, where it became known as Chemo's Ultimate SEO URL's , I guess to acknowledge the lineage from the OsC mod, and as tribute to Chemo.
This was changed and modified to continue working with each new version of Zen Cart by Dreamscape , and in the version 1.3's Dr. Byte did some work on the files.
The version 3 beta is a rewrite to address some of the creaking from the upgrades and shortcomings of the original.
There was another SEO mod for Zen Cart called I think SEO that just works? but I'm not sure of the status, as I've never used it.