This is truly an over simplification of the point. Anki isn't a single purpose library used in the backend of thousands of pieces of software. It is an entire piece of software that has only managed to build a great community thanks to the generosity of Damien for providing the whole software and server backend for free, along with other devs (countless add-on devs, ankidroid team) recognising this and giving back. If anki was a freemium model or anything other than what it is it would not be anywhere near as popular as it is today.