New Linux users who begin to research the operating system will soon across something called GNU/Linux. This is not a Linux distribution, but a somewhat successful campaign by the Free Software Foundation to get many of the more principled Linux users to give credit to the GNU Project every time they mention Linux. The campaign revolves around rather obscure arguments about how to define an operating system and an inexact recollection of both the history and the varied contemporary nature of Linux. The debate can be safely ignored by new and old Linux users, but if you want to know why there is no need to call Linux GNU/Linux, then read on.
The term GNU/Linux sounds to the uninitiated like the name of a Linux distribution, such as Red Hat Linux. It is likely that the original intention was that it would be the name of a distribution. When computer science student Ian Murdock sought help with his 1993 redesign of the earliest Linux distributions, one of the email replies he received came from Stallman of the Free Software Foundation. Murdock was employed by the Free Software Foundation between November 1995 and November 1996 to work on his Debian system, which at some point in that year he agreed to rename as Debian GNU/Linux. There appears to have been a misunderstanding between Murdock and Stallman, with the former thinking that the Free Software Foundation was sponsoring the development of Debian (as it has sponsored other free software projects), while Stallman seems to have regarded Debian GNU/Linux as the official Linux distribution of the GNU Project, which was also funded by the Free Software Foundation. Midway through his year as a Free Software Foundation employee Murdock passed the leadership of Debian over to Bruce Perens, which prompted Stallman to announce on the GNU Announce mailing list in April 1996 that Debian was leaving the Free Software Foundation and that it would no longer be called Debian GNU/Linux. Perens replied that the Free Software Foundation sponsorship was a personal one for Murdock and that Debian did not want to single out just one contributor for financial support. There was an allegation that Stallman was attempting to micromanage the development of Debian, but Perens asserted that Debian remained committed to the principles of the Free Software Foundation. Perens described Debian as "Son of GNU" and in 2021 it is still called Debian GNU/Linux. There would later be a complete breakdown in the relationship between Debian and the Free Software Foundation over the inclusion of a repository of non-free software. The Foundation maintains a list of approved distributions from which Debian GNU/Linux is a notable absence. In 2011 Murdock stated that he abhorred the GNU/Linux terminology, primarily because the wider community had never embraced the term: see Interview with Ian Murdock on Debian’s Early Days.
In the above interview Murdock describes Stallman's suggestion of the GNU/Linux name as an attempt to battle against the increasing fragmentation in the free software movement.
Stallman has continued to campaign for all versions of Linux to be called GNU/Linux, which has harmed his personal reputation and that of the Free Software Foundation. There is a FAQ about this issue on the Free Software Foundation website, GNU/Linux FAQ. The FAQ is refreshingly honest in that it openly acknowledges most of the objections raised by Stallman's demand that all Linux versions be called GNU/Linux. The answers given are, however, often dismissive and lack any nuance. The impression is left that Stallman realised that he made a huge design error in the GNU Project. He set about creating the tools that you would expect to find in an operating system and failed to create the operating system. Beyond Debian and free software purists there are few who deny the obvious point that Linux is the operating system and the GNU utilities are among the many applications that it can run. No matter how much Stallman wants to expand the definition of an operating system to fit GNU and exclude Linux he cannot avoid the basic criterion for an operating system. It must be possible to install it on a computer and have the computer work. There is no GNU operating system, because GNU cannot make a computer work because after 30 years the project has still not managed to develop a kernel that is usable on a production machine, and that is the official position of the GNU project. The problem for the GNU/Linux claim is that the GNU design philosophy was to create free equivalents of Unix applications and then when the components were in place to design a kernel to allow the communication between the hardware and the applications. Without the Linux operating system GNU would still be a collection of free programs that could run on a proprietary Unix operating system. Or alternatively they might have ended up as optional extras in the BSD family of Unix-like operating systems, which Stallman does not see as free operating systems. As history worked out, it was Linux that allowed the free applications of the GNU Project to function in a completely free system. Stallman is quite open the GNU Project adopted other items of free software to add into their operating system and did not seek to write everything from scratch, yet he does not give the same leeway to Linux, which quickly developed a working kernel and found that there was already such an active marketplace of free software development that there was no need to write anything beyond its bare bones operating system.