Industrial MUD 0.2.0
Industrial MUD is a free Multiple User Dungeon Telnet Server that is written from scratch.
It is developed for Linux and includes a small internal programming language called Weld.
Weld allows for artificially intelligent autonomous computer robot players. Customization is definitely possible, but it is ready to run right out of the box.
It is believed to be very efficient in execution speed, system load, memory and binary size. Currently the source code is around 4,000 lines of C code.