“Work began on the Hurd, the true kernel of the GNU operating system, in May 1991, but it has yet to materialise as a production-ready kernel. Richard Hillesley tells the story…

Although the GNU operating system was first conceived in 1983 and the Free Software Foundation (FSF) had first declared an interest in using the Mach microkernel as the core of the GNU operating system kernel as far back as 1987, the sources of the Mach microkernel – developed at Carnegie Mellon University (CMU) – weren’t released under a suitable licence until 1991, by which time Linus Torvalds had begun his project to write a UNIX-like kernel for the IBM 386.

If the Linux kernel hadn’t been written when it was, licensed under the GPLv2 and surrounded by components of the GNU operating system, or Linux hadn’t captured the moment and the imagination of developers, the energy that gathered around Linux might have gone to the Hurd and the world might have been a different place. But it wasn’t just the rise of Linux, or the choice of the Mach microkernel that slowed the progress of the Hurd….. (continued)”

Whatever Happened to the Hurd: The Story of the GNU OS (linuxuser.co.uk)