Integrations without automated solutions are harder than it’s supposed to be 
For example, there’s a possibility to integrate Discourse with ActiveCampaign via connector from Zapier (here’s the documentation on the link ), but it’s really hard to find something relevant regarding Salesforce.
The best way to arrange Salesforce integration via API, especially when it goes vice-versa you should point up a couple of things:
- Does your sfdc cloud support such kind of integration?
- If yes - are there any fields in Salesforce that are mapping the data you would like to sync with Discourse?
- For two-side integration - are those fields mapped equally in both systems, to be understood in case of continuous sync?
Anyway, there’s still a possibility of customized API data sync with Salesforce integration consultants.