I did some digging on this because I'd love an NYCFC Forums app (for push notifications mostly) and it looked like the XenForo developers might be working on a multi-forum app (I.e. Users would be able to sign in to multiple XenForo-based forums at once). Thread has been quiet since late last year though.I'll be reordering stickers soon and will be sure to send them out to every elite donor.
For the App it's something I've always wanted to do but to actually have the website be integrated into a fully functional app I think it will cost a lot. I'm talking getting phone notifications when you get them on the forum and the works.
For now you can always just add it to your home page for quick access.
I think this platform does an outstanding job on mobile browsing and at the moment spending the $$ to develop an app would be a waste.
I have been looking at possible ways to upgrade and at the moment I think the only thing we could use is a nice simplistic redesign.
If any other developers are curious, I'd be down to work on it.