The Free On-line Dictionary of Computing (30 December 2018):

msgGUI

    A graphical user interface for GNU Smalltalk.
   The msgGUI package contains the basics for creating window
   applications in the manner available in other graphical
   Smalltalk implementations.  Version 1.0 of the library was
   by Mark Bush, ECS, Oxford University, UK.

   (ftp://ftp.comlab.ox.ac.uk/pub/Packages/mst/mstGUI-1.0.tar.Z).

   (2000-06-14)