The Jargon File (version 4.4.7, 29 Dec 2003):

Zork
 /zork/, n.

    The second of the great early experiments in computer fantasy gaming; see 
    ADVENT. Originally written on MIT-DM during 1977-1979, later distributed
    with BSD Unix (as a patched, sourceless RT-11 FORTRAN binary; see 
    retrocomputing) and commercialized as ?The Zork Trilogy? by Infocom. The
    FORTRAN source was later rewritten for portability and released to Usenet
    under the name ?Dungeon?. Both FORTRAN ?Dungeon? and translated C versions
    are available at many FTP sites; the commercial Zork trilogy is available
    at http://www.ifarchive.org/. See also grue. You can play Zork via a Java
    Applet.


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

Zork
Dungeon

    /zork/ The second of the great early experiments in
   computer fantasy gaming; see ADVENT.  Zork was originally
   written on MIT-DM during the late 1970s, later distributed
   with BSD Unix as a patched, sourceless RT-11 Fortran
   binary (see retrocomputing) and commercialised as "The Zork
   Trilogy" by Infocom.  The Fortran source was later rewritten
   for portability and released to Usenet under the name
   "Dungeon".

   Both Fortran "Dungeon" and translated C versions are
   available from many FTP archives.

   [Jargon File]

   (1998-09-21)