LMI Lambda?

[Alfred M. Szmidt]

   As for a LispM emulator, personally, what I'd like to do (but don't
   have the resources to do and have other things I'd prefer to put my
   time into) would be to develop an emulator - with a legitimate copy of
   the software to test it against - then work on developing an
   alternative, open, system to run on it.

System 46 for the MIT CADR is licensed under a 3-clause BSD license --
start hacking. ;-) You even have an emulator for the MIT CADR.