GNU has interviews and more clarifying all the way back to MIT AI lab, lisp machines the printers proprietary code triggering free software movement, etc.
- https://www.gnu.org/philosophy/speeches-and-interviews.html
- https://www.gnu.org/philosophy/essays-and-articles.html
Linux just happened because GNU hand't developed a proper kernel yet; Linus wrote that himself on an mail to the Linux Kernel or Minix mailing list IIRC.