If there was one that was working though, I wouldn't really suggest using it(an unofficial app) if it isn't open source, as we wouldn't know what data they're collecting as they would have access to your email and your password, which is something you would really wouldn't want.
AFAIK, it was open source and developed by a trusted user.
Is it even possible for such forums to be turned into an app?
Anything can be done with an API or scraper.