A list of companies involved in producing and/or releasing GUIs:

	Acorn Computers Released RISC OS. Available at http://acorncomputers.co.uk .
	Amiga International Released Amiga OS. Available at http://www.amiga.com .
	Apple Released Apple II, Lisa Office System, Mac OS, Newton OS and NeXTSTEP/OPENSTEP/Rhapsody. Available at http://apple.com .
	AT&T Released OPEN LOOK. Available at http://att.com .
	Atari Released TOS.
	Be Released BeOS. Available at http://beincorporated.com .
	Berkeley Softworks Released GEOS/GeoWorks.
	Breadbox Computer Company Released GEOS/GeoWorks. Available at http://www.breadbox.com/ .
	Commodore Released Amiga OS.
	Digital Research Released GEM.
	General Magic Released Magic Cap. Available at http://www.genmagic.com .
	GeoWorks Released GEOS/GeoWorks. Available at http://www.geoworks.com .
	GNOME Foundation Released GNOME. Available at http://gnome.org .
	Go Corporation Released PenPoint.
	Hewlett-Packard Released Common Desktop Environment and NewWave. Available at http://hp.com .
	IBM Released Common Desktop Environment and OS/2. Available at http://ibm.com .
	KDE e.V. Released KDE. Available at http://kde.org .
	Massachusetts Institute of Technology Released The X Window System. Available at http://mit.edu .
	Microsoft Released Bob, OS/2, Windows and Windows CE/Mobile. Available at http://microsoft.com .
	New Deal Released GEOS/GeoWorks. Available at http://www.newdealinc.com .
	NeXT Released NeXTSTEP/OPENSTEP/Rhapsody. Available at http://www.next.com .
	Novell Released Common Desktop Environment. Available at http://novell.com .
	Packard Bell Released Packard Bell Navigator. Available at http://www.packardbell.com .
	Psion Released Symbian OS/EPOC. Available at http://www.psionteklogix.com .
	QNX Software Systems Released QNX. Available at http://qnx.com .
	Quantum Software Systems Released QNX.
	RISCOS Released RISC OS. Available at http://riscos.com .
	Serenity Systems Released OS/2. Available at http://serenity-systems.com .
	Silicon Graphics Released IRIX. Available at http://sgi.com .
	Sun Microsystems Released Common Desktop Environment and OPEN LOOK. Available at http://sun.com .
	Symbian Released Symbian OS/EPOC. Available at http://www.symbian.com .
	Version Soft Released Apple II.
	VisiCorp Released Visi On.
	X Consortium Released The X Window System.
	X.Org Released The X Window System. Available at http://x.org .
	Xerox Released Xerox Star/ViewPoint/GlobalView. Available at http://xerox.com .