uniData and uniVerse were competing companies that provided an operating environment designed after the PICK Operating Syustem. They merged ~5 years ago to form Ardent Software. Ardent was bought up by Informix, which in turn was bought 2 years ago by IBM. uniBasic is the proprietary language used by that system.
Pick Systems, the original purveyor of the system, merged with Raining Data a few years ago. You can find detailed info on the current product offerings at: www.RainingData.com
The Raining Data product is called D3 (D-cube); Omnis is totally seperate. D3 is still available as a native O/S for x86 systems, as well as several other platforms.
IBM has renamed the PICK-like products U2 and you can find product info at: http://www-3.ibm.com/software/data/u2/
The Informix product is a totally seperate design from the U2 products, which still have seperate links on the site for uniData and uniVerse. Both of these systems originally ran on Unix (and variants), but uniVerse, I know, runs on several Windows platforms.
Don't know about finding customers. Database Trends and Applications is a monthly (free) magazine that specializes in PICK-like systems. Get info at: http://www.dbta.com