Author here. As you say, it's a highly-compressed version of history. Getting into the finer points of the evolution of open source wouldn't really have had any bearing on the rest of the article.
"When we call software “free,” we mean that it respects the users' essential freedoms: the freedom to run it, to study and change it, and to redistribute copies with or without changes."
The bigger part of the "how we got here" was actually that GitHub ended up creating this ecosystem where collaboration was so open and easier to use to a larger population that we ran into an unintended consequence: maintainers being overwhelmed.
The overall history was intentionally a very quick, broad brush stroke to move into the points that pertained to someone feeling like they had to close their project to contributions.
Also, this is your readme so it’s not like you have some editor pressuring you to cut down.