CoffeeMud is a text-based virtual reality game engine (a MUD). It is a mature, full-featured Java codebase. It includes web (HTTP) and email (SMTP) servers, chat (IMC2 and I3) and web clients, and supports ANSI, MXP, and MSP.
VRS is an environment for presenting three dimensional (3D) world. All visualisations are made at client(s) side VRC (Virtual Reality Client - example client is under developement, SF site avaible, see also http://jvrc.info).