But it literally is the same. The only difference is the user space. Debian GNU/kFreeBSD shows this. Different operating system same user space.
Take a look at Wikipedia for more info.
An operating system (OS) is system software that manages computer hardware and software resources, and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, peripherals, and other resources.