[I originally asked the following on Twitter which was probably not the smartest idea]

I was recently wondering about the origins of Linux, i.e. Linux Torvalds doing his MSc and deciding to write Linux (the kernel) for the i386 because Minix did not support the i386 properly. While this is perfectly understandable I was trying to understand why, as he was in academia, he did not decide to write a “free X” for a different X. The example I picked was Plan 9, simply because I always liked it but X could be any number of other operating systems which he would have been exposed to in academia. This all started in my mind because I was thinking about my friends who were CompSci university students with me at the time and they were into all sorts of esoteric stuff like Miranda-based operating systems, building a complete interface builder for X11 on SunOS including sparkly mouse pointers, etc. (I guess you could define it as “the usual frivolous MSc projects”) and comparing their choices with Linus’.

The answers I got varied from “the world needed a free Unix and BSD was embroiled in the AT&T lawsuit at the time” to “Plan 9 also had a restrictive license” (to the latter my response was that “so did Unix and that’s why Linus built Linux!”) but I don’t feel any of the answers addressed my underlying question as to what was wrong in the exposure to other operating systems which made Unix the choice?