Also known as the XForms library. This is a
C library
providing a toolkit interface over
Xlib. It's been
around for quite a while, and is still in use by
several projects. The most famous of these is
LyX.
XForms, while considered by most to be far superior
to its contemporaries Xt and Motif, is showing
its age in comparison to modern toolkits such as
Gtk and Qt. In addition its current closed-source
status is drawing criticism.
However the authors have stated they plan to release
the next version under the GNU General Public License
or similar open-source license.
http://world.std.com/~xforms/