Neither you nor I nor the original author have hard numbers about who knew what, so all of this is conjectural. But I was addressing a different point, which wa

Neither you nor I nor the original author have hard numbers about who knew what, so all of this is conjectural. But I was addressing a different point, which was my difficulty in reconciling the author's position that "a developer from 1975 could ... feel pretty comfortable" with modern programming languages because the underlying techniques existed already "in some form", while also implying there would be no developers from 1975 who would feel comfortable with version control control and library ecosystems "in some form." It's surely true that not all programmers now know about closures, just like it's unlikely that all programmers in the 1970s knew about them, so this isn't a universal claim. Nor did I think it was a universal. Rather, I think the author's point is that those with interest and experience in programming languages would have known the topics. That is undeniably true. My response was to point out that those with interest in software engineering techniques would have known about version control systems and library ecosystems "in some form", because I can point to people who were SCCS, and people who were involved in library ecosystems. "Python isn't suitable, or at least is arguable a poor choice, for some tasks." That inarguable. Java isn't suitable for some tasks either. Nor is the statement that the C standard library is smaller than Java. But why is it that Java's standard library "really kicked off the trend of wide scale reusability"? What was the size magic threshold? Why did previous languages with a large set of standard libraries (I suggested Object Pascal, eg, from Turbo Pascal 5.5) not kick off that trend? "There also wasn't a good way to distribute" Again, I don't think you are discussing the same point I am. The author wrote "The magic part is simply that open source licenses like Apache and MIT lower the friction to trying out a new library." My point was that in the 1970s that magic part wasn't relevant. Instead, and I agree with you, the "magic part" for a 1970s developer is instant network access, and not open source licenses. I think licensing is much less magical... and even in the 1970s there was already ARPAnet, email, and UUCP, so again it's more a diffusion process than something "magical" or unknown in 1975.