> It seems to me that developers back in the 80's (at least in the PC / home computer world) were quite possessive... even for hobbyist projects that they gave away for free.
Yup, this is one of those things where the free software movement managed to be surprisingly influential, even before open source proper was a thing. People who were committed to releasing freeware stuff, with no delusions about ever selling it commercially (even as indie "shareware") started making their source code available and using free software licenses, often "share alike"/"copyleft" ones. Even Linux itself went down that very path, in fact.
Yup, this is one of those things where the free software movement managed to be surprisingly influential, even before open source proper was a thing. People who were committed to releasing freeware stuff, with no delusions about ever selling it commercially (even as indie "shareware") started making their source code available and using free software licenses, often "share alike"/"copyleft" ones. Even Linux itself went down that very path, in fact.