How many people bought Dwarf Fortress?

I'm curious, have you got any idea about the popularity of the game Dwarf Fortress? Specifically, I'm wondering, how many individuals have actually purchased and played this game? It's been around for quite some time now, and I'm intrigued to know just how many people have embraced it. I'd be fascinated to learn more about its player base and how it's fared in the market over the years. Do you have any insights or estimates on the number of Dwarf Fortress buyers?