Hi,
Why? Apache is not GNU software, but it clearly qualifies as free software in the sense of Stallman, just not as copyleft , nor as compatible with the GNU GPL.
it is true that GNU/Linux system is not identical to all software from GNU Project plus Linux kernel. Many software in public domain could be also a part of GNU/Linux as an operating system, like TeX.
On the other hand, a "Pure GNU/Linux" with only GNU tools and Linux kernel could reside at the original point of the spaces, with the criteria as the dimensions we are discussing, we could put the current distributions into various "clouds" we constructed spaces. And finally we could measure the "distance" how far a distribution from the original point of the space, sth like Minkovsky distance, just possibly with more dimensions other than 4, and the weight of each dimension could not be the same.
Best, Frederic