I'm actually rather shocked that an article this long, and well-written, and useful, makes only one offhand, passing, "oh by the way" reference to the "GNU tools".
Were it not for Stallman and the GNU team dedicating their professional lives to generating a FOSS equivalent (and IMO improved flavor) of UNIX, Linux would have written his kernel and have nothing to show for it (maybe something via MINIX and Andy T. but still...).
On the flip-side, were it not for Linus's kernel, the GNU software would still be waiting for the Hurd to become useful.
Good article, no problem there. But let's give Stallman et al their due.