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?]