That website uses NodeBB, which does indeed incorporate a lot of the same concepts as Flarum and Discourse (in terms of how they view "modern" forums, not code-wise). There's quite a lot you can do with Flarum, as well as the other options; the possibilities are vast, especially if you indeed have a strong developer.
A downside is that Flarum is still very much in beta and is still growing, so there's not quite as many established developers putting out extensions and working on the core software as you'd find with other forum systems. Though, with a developer, that may not even be an issue for you.
