I think forums are the one type of website that's simply impossible to make with Ruby on Rails. In fact, I don't think any web framework can handle it...
I think your best bet in this instance is to code everything directly in binary. That's what I would do
Sure, but there are a gazillion forum websites already. I'd just use an existing one. The one D uses is the best I've ever used. I think it's actually written in D, which is a very niche language but way nicer than Ruby.