CDS/ISIS: tell us more

I've now seen CDS/ISIS and its variants mentioned in several places and am still confused about what it is but here's a brief description nonetheless. from the UNESCO ISIS page: Micro CDS/ISIS is an advanced non-numerical information storage and retrieval software developed by UNESCO since 1985 to satisfy the need expressed by many institutions, especially in developing countries, to be able to streamline their information processing activities by using modern (and relatively inexpensive) technologies. The software was originally based on the Mainframe version of CDS/ISIS, started in the late '60s, thus taking advantage of several years of experience acquired in database management software development." take 2, from the CDS-ISIS user forum site: "Mini/Micro CDS/ISIS is a text retrieval program, designed and distributed free of charge by UNESCO. It is widely used for bibliographic (and other) databases throughout the world, and especially in developing countries." If I understand all this properly, it is basically a non-relational database environment commonly used by libraries and other largely nonprofits (20,000+ of 'em) throughout the world. I pulled down the unix version but can't quite make heads or tails of it. Somebody please explain more... update: collected comments from all who offered are available here.