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

X Consortium

   A vendor consortium supporting development, evolution and
   maintenance of the X Window System.  The X Consortium is an
   independent, not-for-profit company.  It was formed in 1993 as
   the successor to the MIT X Consortium, a research group of
   the MIT Laboratory for Computer Science.

   (ftp://ftp.x.org).  (http://x.org/).

   [Members?]