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.
VRMoo can be summed up as such: Virtual Reality Object Oriented MUD. I intend VRMoo to be capable of simulating complex environments, allowing real time 3D interaction with these environments, and allowing real time 3D interaction with other users.