Before we get all complicated, I will go ask some people if they have the source.  :-)

I was the first person to die on AberMUD, and that particular story is told here:

  https://dropsafe.crypticide.com/alecm/abermud/README_HISTORY.HTML

...along with a walk-through of the room descriptions from that era, respun as simple navigation through clickable room descriptions.

I didn't go into the topic of this because it seemed a little far off the topic of "Unix", but if Warren will permit me a brief digression, some of which many of you will be completely aware, but this is for posterity:

Over here in Europe the Internet was not king; instead the UK universities were linked by X.25 networks, the hostnames were bigendian, and the services often literally chargeable.

The UK academia network was JANET (Joint Academic NETwork) and - since systems could not communicate with each other unless a godlike "Network Manager" waved dead chickens over them in arcane ceremonies - the students wrote, and then advertised, samizdat style, the addresses and login credentials for various "Bulletin Boards" which they would log into and share messages.

Onesuch was University College London (UCL) "Bullet", run by myself, Rob Newsom, and Steve Usher, at UCL.

Steve keeps a copy of Bullet running even today, the history and details are at: https://www.earth.ox.ac.uk/~steve/bullet.html

At Aberystwyth - where I got a job after graduation, having hacked it quietly but extensively - was Honeyboard, running on the previously mentioned L66 under GCOS-3.  Authors: Alan Cox (of Linux fame) 

Both Bullet & Honeyboard had "message boards" (cf: single-host USENET) and "talkers" (group chat & private messaging) - the irony was that Bullet was meant to be a MUD but turned into a Bulletin board, whereas Honeyboard was a bulletin board which turned into a MUD - AberMUD.  

In the latter case: "descriptions" (flat files, named by channel number) were added as augmentation to numbered "talker channels", and the files were given annotations ("#DEATH" - kills people on entry, logs them out) in rooms with special features; then a basic action parser was hacked into the chat system; the rest of *that* story is in the README_HISTORY.HTML link, above.

Honeyboard became AberMUD, got enhanced with a lot of cleanup, then got shared, and - this is where I get hazy - Rich $alz got a copy, reworked a bunch of code (ported to C at this point? Or maybe earlier) and it got posted to USENET... and the rest is more well-known history.

I'll send this now, and then forward the e-mail around some friends to see if the source is extant.

    - alec

* footnote: we shared addresses of BBSes samizdat style amongst friends; one very popular place to do that was Essex MUD, the source code for which is upstream.  A TOPS-10 system, it permitted access to players from (IIRC) 2am until 7am on weekdays, plus extensions on weekends.  I lost a lot of sleep that way.