Pre internet links are hard. I grew up using these versions of open source.
IBM SCO and sun formed Open source licences that were very literally you got to see and change the source.
In the 60 as CPU tech was a minefield of different ideas and architecture. It was the only way companies your keep up with mainframe PCs.
You will need to go to a library with microfiche and hubd down the 1960s open source magazine if you want more then actual old farts telling you the truth,