There is a point and your confusion is frequent one. Let me clarify.
When a economist like the author uses uses the word 'monopoly', it's shorthand for 'monopoly power'. It's obvious from the context of the discussion what he means. The confusion arises when people know the definition of pure monopoly (single supplier) but don't know what is monopoly power.
Between pure monopoly and perfectly functioning markets there is a large area with varying degrees of monopoly power.
There are different ways to quantify the monopoly power. One is using market power and Lerner index. In perfect markets Lerner index would be zero. In practice it rarely is. https://en.wikipedia.org/wiki/Lerner_index
Internet economy generates large companies with monopoly power trough the network externalities. Dominating companies create barriers to entry for newcomers. If the value comes from being connected to others, the platform that connects gets most of it's value from the number of customers and economies of scale, not from being technically better. (of course, after you have the economies of scale you can hire the best people to keep up).
Classical Natural monopolies like railway systems, telephone and electric networks are often regulated to preserve markets. Platform economies have similar attributes.
In fairness to Hanson, a natural monopoly is distinct from a “monopoly” in the popular sense. Public utilities are often natural monopolies—for instance, a city might have only one power company because it doesn’t make sense to build the redundant infrastructure for two power companies. Doing so would incur a high, unnecessary fixed cost. [1] I think Hanson’s trying to draw an analogy to such firms, though I find it a bit loose.
Open source software development absolutely has a purpose. Licensing absolutely has a purpose. But generalization is a well-known cost for those in tech, and marketing is a well-known cost at general.
I can't understand this. Google, Amazon, Facebook, Apple, Oracle, Microsoft, countless others, all have their own huge backroom IT software projects.
Which one of them is supposed to have a monopoly on it?
People just seem to throw around 'monopoly' to mean nothing more than 'some large number of companies are able to achieve some things that others aren't'. Some other people just seem to use it for 'company that I think is too successful'.
There's no point in the word any more.
I think part of the problem is people feel free to define the group that can have a monopoly in any way they want. Is the intention here that 'large talented companies' have a monopoly on backroom IT software? If we're going to define groups however we want I can say things like 'people who are good at football have a monopoly on playing football professionally'.