DevMUD (I like that name better, and it apparently hasn't been used)

Summary of in-game language stuff.


More than one, possibly simultaneously.


VM-based -- byte-code (word-code?) assember, and compilers for
language du jour

bytecode -- don't waste opcodes.

(actually, an assembler format could give bytecode-independence)  Changing
the VM doesn't necessarily require recompiling.

verifyer?

strong/weak typing
variable scope and extent?  (GC, etc)

 >Primitive data types to be represented.
 >Complex data types (object).
 >Control structures.
 >Looping structures.
 >Subroutines/procedures/functions.
 >Label generation.
 >Symbolic storage.
 >Variable storage.
 >Type conversions/promotions.
 >Native routines call and return format/native symbol table.
 >Sub progam/module call and return protocol.
 >Exception handling/trapping
 >Arithmetic processor.
 >Booleans/conditionals.
 >Operator precedence.

defining the boundaries clearly is important

syntax?  For a VM, not that important.

Use one (or more) of the several readily available embeddable langs.
Python
Perl
TCL
Guile


Lisp-like
forth-like


Should be able to fake System modules with VM code modules.
