Yes the users are quite active. The main thing people are paying for are the video features and the video scraper. There is some code which allows the app to pull videos from youtube, instagram, facebook, twitter, reddit, etc, and I think that is really the thing that separates this app from other generic image editors.
Oh sure, YouTube forbids that. Once there's enough traffic to care, it'll get cut off. But YouTube is somewhat unlikely to try to sue one's socks off for breaking the ToS. Copyright owners though...