From 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)">(ftp://ftp.x.org). http://x.org/)">(http://x.org/).
[Members?]