Yes, but what is this supposed to prove? That proprietary software is more popular? Usually it is. There are many different reasons for that, but one of them is that there is simply more of it.

It’s also a game, so there is no productivity gain or loss associated with it. There is no on call IT support, but you also don’t need any and if something breaks, you lose nothing except the ability to play THIS game for a short while. It’s not a… webserver you run your online shop through where every hour of downtime costs you X hundreds of euros or dollars.

It's similar to selling a desktop app or a mobile app. I can't find the source code of AnkiMobile right now, but I'm pretty sure it's Free Software. If you want an example of a commercial app that people might use to do work, there is Ardour.