Evennia MUD/MU* Creation System 
Evennia is a modern library for creating online multiplayer text games (MUD, MUSH, MUX, MUCK, MOO etc) in pure Python. It allows game creators to design and flesh out their ideas with great freedom. Evennia is made available under the very friendly BSD license.
http://www.evennia.com is the main hub tracking all things Evennia.
Features and Philosophy
The Evennia library aims for you to have a fully functioning, if empty, online game up and running in minutes. Rather than imposing a particular style, genre or game mechanic we offer a framework on which you build the game of your dreams. The idea is to allow you to concentrate on designing the bits that make your game unique.
Coding in Evennia is done using normal Python modules imported into the server at runtime. All library code is heavily documented and Evennia comes with extensive manuals and tutorials. You use Python classes to represent your objects, scripts, players, in-game channels and so on. The database layer is abstracted away. This makes it possible to create the game using modern code practices using the full flexibility and power of Python.
Evennia offers extensive connectivity options, including traditional telnet connections. Evennia is also its own web server: A default website as well as a browser-based mud client (html5 websockets, with fallback to AJAX) runs by default. Due to our Django and Twisted foundations, web integration is easy since the same code powering the game is also used to run its web presence.
Whereas Evennia is intentionally empty of game content from the onset, we do offer some defaults you can build from. The code base comes with basic classes for objects, exits, rooms and characters. There are systems for handling puppeting, scripting, timers, dynamic games states etc. A default command set (completely replaceable with your own syntax and functionality) handles administration, building, chat channels, poses and so on. The default setup is enough to run a 'Talker' or some other social-style game out of the box. We also have a contributions folder with optional plugins and examples of more game-specific systems.
Current Status
The codebase is currently in Beta. While development continues, Evennia is already stable enough to be suitable for prototyping and development of your own games.
Where to go from here
If this piqued your interest, there is a lengthier introduction to read.
To learn how to get your hands on the code base, the Getting started page is the way to go. Otherwise you could browse the Documentation or why not come join the Evennia Community forum or join us in our development chat. Welcome!