This forum is a Discourse instance that’s not tied to any Open edX instance. Discourse is open source, but tCRIL pays for a hosted solution for this particular site–the Business plan, at $300/month.
Open edX can act as an OAuth2 provider, so it’s possible to configure your Discourse instance to use your Open edX site for authentication. That would give you the basic auth-level integration.
I don’t know what your options are for deeper levels of integration like cohorts that mirror Open edX groupings. While he was the product owner for TNL at edX, @marcotuts pushed for a vision where top level forums like these are a more natural part of the Open edX experience (instead of only having the per-course ones that are built-in today), but I don’t know how much of that supporting infrastructure was designed or built.
@xitij2000 might know more about the latest state of Discourse integration with Open edX. Much of the focus of that thread was around making Discourse a viable solution for per-course discussions, but there may be some general Discourse integration work as well. I believe that OpenCraft did some kind of integration with Discourse for LabXchange, but again, I’m not familiar with the details.
Tagging a few folks that might know more: @jristau1984, @Agrendalath, @braden, @gabrieldamours