You have totally skipped the contributions of Free Software Movement and the GNU project. The GNU Project started way earlier in 1984 when lead by Richard Matthew Stallman a team of volunteers started making a Free Software (Free as in Free Speech) clone of the Unix operating system. The operating system consists of a lot of parts, a lot of unitilites, low application programs and programs which are written written by combining those programs. Linux is the only the kernel which was included in the GNU/Linux operating systems in 1991. A kernel is a software which interfaces the hardware and low level application programs. A kernel is absolutely useless an Operating system and that is why FSF encourages people to call the OS GNU/Linux to give them due credit.