Earlier quoted context omitted.
There’s no such thing as a tiny monopoly.
An example of a tiny monopoly would be a program with no alternatives that performed a task worth a few thousand bucks to 20 people on Earth. It doesn't have to be Standard Oil for monopoly pricing to take effect, if the market is small enough the mere fact that two vendors couldn't survive at the same time would be enough to keep out competition. Another example would be proprietary data formats, if your program is…
A monopoly occurs when competition is actively prevented, in spite of its ample competitive ability. The monopolist uses its power to block the entry of new competition, even if that competition has the product, know-how and so forth. In some cases monopolies are geographical, like utility companies. Another utility company is just as capable, but it and its wiring/plumbing is in another district.
The mere difficulty of mustering a viable competitive effort (e.g. it being difficult to write a replacement program that those 20 people are willing to use instead) is not a monopolistic entry barrier.