See termux app's addons and some simple mobile tools apps for Android. They have paid versions on play store which are actually open source. But you are paying

See termux app's addons and some simple mobile tools apps for Android. They have paid versions on play store which are actually open source. But you are paying for the privilege of getting them on play store instead of compiling them and loading through adb. Another way is providing an SaaS version, but having an open core product is better for this. If memory serves right, wallabag does something like this. Enterprise support etc: There are quite a few companies that provide support for software. Red Hat for example. Bounties: see bountysource