[Last modified: Jan 02]

Answer: Motif is a widely-accepted set of user interface guidelines developed
by the Open Software Foundation (OSF) around 1989 which specifies how an X
Window System application should "look and feel". Motif includes the Motif
Toolkit (also called "Xm" or the "Motif widgets"), which enforce a policy on
top of the X Toolkit Intrinsics ("Xt"). Xt is really a "mechanism not policy"
layer, and Xm provides the specific "look and feel". For example, Xt does not
insist that windows have titlebars or menus, but it provides hooks for
developers of specific toolkits (Motif, OpenLook, Athena widgets) to take
advantage of. In addition to widgets, Motif includes the Motif Style Guide
document (as well as several others listed in my FAQ) which details how a
Motif user interface should look and behave to be "Motif compliant".

The X Toolkit Intrinsics are built upon the lowest programming level API
called "Xlib" (X library). Both Xlib and Xt are specified by the Open Group
(formerly called the MIT X Consortium), which you can reach at:

    http://www.camb.opengroup.org/tech/desktop/x/

In early 1996, OSF merged with X/Open to form the Open Group.  At the
beginning of 1997, the X Consortium closed and transfered ownership of its
projects to the Open Group.  The Open Group continues development and support
on the X Window System, Motif, CDE, and other technologies.

On May 15, 2000 the Open Group released the Motif source code, using a public
license, to the Open Source community.  The current version of Open Motif 2.2,
which was released January 29, 2002.  For more information, see:

    http://www.opengroup.org/openmotif/
    http://www.motifzone.net/