I've been reading through an old-ish book on MUMPS ("M Programming", by Walters) to try and get some historical perspective on the language. The book was published in 1997, and provides the following list of then-extant vendors (I don't know whether this is exhaustive):
- InterSystems M (for Windows 9x/NT)
- InterSystems Data Tree M (for Windows 3.1 and DOS)
- Micronetics Standard M (for Windows 3.1/9x/NT and UNIX)
- InterSystems DSM (for VAX, VMS, and UNIX)
- InterSystems Open M (for VAX, VMS, and UNIX)
- PFCS (for UNIX)
- GT.M (for UNIX)
In the 18 years since, most of those MUMPS implementations have ceased to be; GT.M is the only one to have survived (albeit under new stewardship). However, the market leader today is an InterSystems product, albeit one that did not exist back in 1997: Caché. (Yes, the name is terrible, and I hate whichever bozo decided this would be an acceptable name for a programming language.)
What is the "genealogy" of Caché? Is it a direct descendant / rebranding of one of InterSystems's older products? Wikipedia claims without citation that Caché descends from ISM (the first entry on the list above); is this accurate?