After seeing your note, I thought, "damn, I've used AntennaPod a LOT, I'll donate!"
If you go to donate they basically say that all their costs are covered right now, but ask if you can help in non-financial ways (translations, help on the forum, beta test, code if you can, spread the word, UX work). I'll be honest, that level of transparency makes me love the app more than I already did!