Not only the game is free, but it also allows contributors to earn fiat or crypto in various ways. It's easy to get involved in the community or contribute to the project directly. Also, it's a great project for getting experience as a coder, artist, game developer etc. in order to build up your portfolio. The source code is publicly accessible so you can study it and make your own projects. Besides all that, the project can serve as an example that you can have a free open source project and still be financially viable, since we're generating a steady income already from sponsors by offering them clickable avatars plus the project has  big potential to generate income in many ways without affecting gameplay in any way.