I'm sorry but what if a user don't have an API Key? ç__ç
Does it has your API key in the app? In that case, please delete the download links until you haven't found a solution that doesn't reveal your API key with a simple http analyzer.I modified the Jar file to work with the user API keybut, by the way, check out https://github.com/TheHowl/OsuLevelCalculator - you could use it to say the score needed for the next level!
But anyway, this app looks very good!