Mark Andrews <mark@alias.com> says:
  You can disable the Indigo Magic environment in two ways:

  1) If you wish to disable it for all users on the machine:

         chkconfig desktop off

  2) If you wish to disable it for a specific user, do

         touch ~<username>/.disableDesktop

     You may also have to remove the ~/.desktop-<hostname> directory as
     well as 4Dwm looks in there for a 4Dwmsession file which it uses
     for a guide to redisplay windows left open from the last session.

     Method 2 works ONLY if you have the original IRIX 5.2 xdm Xsession
     file, which contains the following code chunk:

     if /etc/chkconfig desktop ;
     then
             if [ -x $0.dt -a \! -f $HOME/.disableDesktop ]
             then
                     exec $0.dt $*
             fi
     fi

  If you only want to turn off the file manager, create the file
  ~/.desktop-<hostname>/nodesktop.

  Whether you disable the entire desktop or just the file manager, you
  may also want to set one or more of these resources

     4DWm*SG_autoSave:       false
     4Dwm*SG_manageSession:  false
     4Dwm*SG_useBackgrounds: false

  which are explained in the 4Dwm(1) manpage. See also the desktop_eoe
  release notes.