It sickens me that people bitch and banter at people using supposedly free art, whine even more at poor art, and don't do a single thing to direct people to better development. If a person has enough patience to put said art together, even as placeholders, and progrsm everything themselves then what is the problem? The OP asked for help on resolving an issue with stolen content and gets bashed as a result. Quit being toxic about everything for once in your lives. It's sickening.

Back on topic, if they are using your sources, the best thing you can do is chsnge your hub password as said before, ignore it, and keep developing. If it's closed-source, release a big update that will take too long to copy so they can't keep up. Ideas are only worth so little because those who try to copy them don't have as much resolve as you to see it through. Ignore any interference, protect your things better next time, and keep on producing content.