[dryfish]

From the README:

> For users who can't spend the money, we made it easy to build the pro version from the source code.

[bitwize]

This is actually how I released mobile games in the past. The binaries were for sale on Google Play, whereas the source was open and available for people to compile themselves if they wanted.

I may be revisiting this because Android is now requiring AABs for all Google Play apps.

[lasagnaphil]

And by the way the license is MIT, so there aren't even any worries about modifying the source and incorporating into your proprietary project.