Today, most fonts in practical use are open source fonts. When someone chooses a font for a web project, they typically pick something from Google fonts, which are all open source licensed. Android, the most common OS, uses open source fonts like Roboto by default which are also open source.
The article does not mention open source at all, it has one mention of Google Fonts which is kinda misleading ("the latter of which gives away fonts for free" - well, not really, many of these fonts are not from google and were already free, google is just providing a font hosting service).
An accurate statement would be one company dominates the proprietary font market, which is however only a small share of overall font use.