OK, now I’m following. Discourse, the software, is free. You can follow our official install instructions to install Discourse on a server of your choice. Note that if you don’t already have a server you’ll need to pay for one, for example via Digital Ocean.
Regarding discourse.org hosting, we do offer free plans to open source software developers and crowdfunded groups at free.discourse.group. If you qualify for one of our free plans, submit an application on that page.