Thanks for the link to the API. It looks like it will be quite easy to integrate it with Discourse.
I think that integrating Discourse with WordPress membership plugins is something that will be useful. What I would like to do is create a general wp-discourse-membership plugin that will work with all membership plugins when using wp-discourse and Single Sign On. It will still require you to manually add members to the appropriate Discourse group when they sign up for a membership on WordPress, but it will let you add the member to the Discourse group from the WordPress dashboard, before they exist as users on Discourse. I’ll try to get this done by early next week.
Once that is done, it should be quite easy to customize the plugin to hook into specific membership plugins, so that members are added to Discourse groups automatically at the time that a new membership is created on WordPress.
What is your timeline for getting this up and running?