Discourse - A platform for community discussion. Free, open and simple.

Discourse is easily the best community management tool available currently. It's fast and is simple to use.

I have to stress how much I love Discourse. It's the best forums experience ever.

Happy using it for my projects:

Eve.QA - easy and expressive Q&As for events.

Oprium.com - a place to share and discover exciting opportunities.

Apteka.TJ - forum on health, beauty and family well-being.

Pros:

Robust and modern FOSS forum engine.

Great core team and friendly community.

Powerful full-text search, good plugins and easy to customize.

Cons:

Currently cannot:

- assign moderators and staff per-category;

- let login with phone # (i.e. without email) out of the box.

It is not free. Why does the description say free then?