Can I add additional module to drupal distribution (all inclusive)? I have a SSO module I need to add to Open Social distribution. Can I add this additional module to the distribution (all inclusive)?
In your installation you can add the module just like any other module yes.

If you want to add id to the distribution itself, you would effectivly make a new distribution based on Open Social with the module added - please read the guidelines here to learn how to add it.