By default any user can view the forums as long as page and feature instance view settings are set to all users.

By default only authenticated users can post in forums. Though there is a setting to allow anonymous posting.

Only users with edit permissions on the page or feature instance can get to settings, and you can lock even roles with edit permissions out of settings from the site permission "Roles NOT Allowed To Edit Feature Instance Settings.

Users can edit their own posts for a period of time determined in forum settings.

Users with edit permissions on the page or feature instance can edit or delete any posts or threads.

Hope that helps,

Joe

That is done by integration with Janrain Engage, in Site Settings under the Security > OpenID tab you can click the button to setup Janrain Engage. Then at the Janrain site you can configure which providers are enabled. For example using Facebook or Twitter also requires you to get an application id from Facebook or Twitter before you can enable them.

Hope that helps,

Joe