Obviously I'm missing PennMush?. Muq and Interlude also probably rightly belong to this mud family.
Cool++ exists and is a C++ rewrite of Cool. POE has been renamed to Mica. It's also a wild guess that POO was inspired by MOO.
Anyone know the derivation of PennMush? and it's release dates?
TinyMud? 1.4.1 - released on comp.sources in December 1989 TinyMud? 1.5.1, 1.5.3, 1.5.4 and 1.5.4f also exist Monster released in 1988
TinyMud? was released to some friends of Apsnes as early as August 1989 which explains how several Tinys were running prior to Dec 89.