It's just Linux. GNU is unrelated to Linux, which is a kernel developed by Linus Torvalds. Linux can be used entirely without GNU software in userspace, and the kernel can be compiled without the use of GNU tools. Just because GNU tools were used to initally develop and compile the kernel, and were initially the only available tools for userspace, does not make this true today, and it never made GNU a part of Linux itself at any point of time.
Where are all of the other forward-slashes for every other piece of software on a Linux-based system which makes it just as usable? If a system is running "GNU/Linux", it should be using more than a single forward-slash when there is more to the system than only GNU.