I've noticed a trend lately with open source projects, notably Godot and Blender, having visually impressive release notes. I hope this trend continues.
The author isn't saying that selling is necessary only to make money. At the end of the article he says "But the word "sell" doesn't necessarily mean what you think it means", which then leads to the aside:
"you can either do it in such a fashion that people can indeed build on what you've done, or you can do it in such a fashion that the next person has to essentially duplicate again what you've done"
One thing I commonly see with projects like this targeting developers is they lack code examples on their homepage. Show me some code! I want to see right away what you’re doing differently than all the other libraries/frameworks.