19 Dec, 2016, SlySven wrote in the 1st comment:
Votes: 0
Currently Mudlet allows the user to have multiple profiles active simultaneously even though the main application is single-threaded. Each profile runs it's own Lua sub-system which are currently sand-boxed from each other. I'm currently trying to add limited inter-profile communication based on our Event system which allows the passing of a set of variable arguments {strings/numbers/nil/booleans} between them. Right now we are looking for places where we can test this in a live situation but TMC search facilities have only slightly helped in that it gave TempusMUD (although at least that site has them - the tag based system here is not at all helpful if the tag you are looking for on the MUDs page e.g. "multiplay" does not exist 8-( ).

So does anyone know of any others?
19 Dec, 2016, agda wrote in the 2nd comment:
Votes: 0
I believe NannyMud allows multyplay. mud.lysator.liu.se 2000

It will not possible with inter-profile communication between 2 different muds? If it will,
you could pick two different muds to test against ;)