I'd presume so based on reddit sync (monitization primarly from ads and iap). Apollo's dev at one point made another app (primarly for killing amp links) that was paid and open sourced it, however he had issues with low effort copycats.

https://github.com/christianselig/Amplosion

The bright side of a closedsource app is in certain cases it can encourage faster development since the dev can work on it part/fulltime (idk how syncs revenue worked).

To be clear the post above is my personal view (I could be completly wrong).