If SSO isn’t being used, there are no technical limitations to doing this now. The biggest problem that I see at the moment is sharing the forum’s admin API key. I’d like to make a few changes to the plugin to make it clearer that it can be used with a regular user’s API key. When this is done, all posts from WordPress will be published under the username of the user who’s API key is supplied. Different websites can use different user’s API keys without a problem.
When using multiple WordPress sites with a single forum, if a webhook is being used to refresh comments, a webhook needs to be configured for each WordPress site.
If multiple sites are connected in a multisite setup, the issues with the admin API key, SSO, and webhooks are all taken care of by the plugin - they are all configured on the Network Plugins screen.