GNU/Linux is a free system--not just a collection of useful programs--because the
GNU Project set out to make it one.
RMS found, wrote, or found people to write everything required.
FSF wrote essential components, such as the
assembler and
linker (you have no system without them).
In the 90s the
FSF had put together the whole system aside from the
kernel, and they are still working on a
kernel, the
GNU Hurd, which runs on top of
Mach.
See BSD/Linux.