I would say that open source as a movement sprung up from the principles of early netiquette[0]. Which themselves were built on the foundations of sharing your knowledge with your peers.
Whether you were trawling Usenet or just a presence in your local BBS scene, "teach it forward" was always a core concept. Still is. It's difficult to pay back to the person who taught you something valuable, so you can instead pay it forward by teaching the lessons - along with your own additions - to the later newcomers.
Of course the Eternal September changed the landscape. And now we can't have nice things.
I think the big move to formalization of GNU was that no free compilers for C existed. RS rightly saw this as a problem and did what he thought was needed to get a universal free c compiler.
Whether you were trawling Usenet or just a presence in your local BBS scene, "teach it forward" was always a core concept. Still is. It's difficult to pay back to the person who taught you something valuable, so you can instead pay it forward by teaching the lessons - along with your own additions - to the later newcomers.
Of course the Eternal September changed the landscape. And now we can't have nice things.
0: https://en.wikipedia.org/wiki/Etiquette_in_technology#Netiqu...