Xenforo is the state of the art in terms of forum software but it's not open source (it requires a rather pricey license fee). For something on the free end, s

Xenforo is the state of the art in terms of forum software but it's not open source (it requires a rather pricey license fee). For something on the free end, simple machine forums works on most shared hosts (and in terms of selfhost, it's just a PHP + MySQL stack) and should work for most communities. It doesn't require a lot of technical skill to configure/use, which can make it appealing if you don't want to micromanage mods - they'll be able to figure out the interface themselves. Discourse is popular in tech communities, but I've always found the software to be rather unwieldy and inefficient. It's a ruby dinosaur with all the limitations and advantages that implies. It's also an application that basically demands the "ownership" of an entire server - the devs are explicitly against running other things on the same server that runs Discourse, which is a dealbreaker if you don't have a good budget.