If you are using MODx, the integration of Question2Answer is pretty simple. Enjoy!
The short tutorial and demo is on Leofec.com
Just replace user.php and qa-external-users.php before installing.
The MODx discussion on the topic
Has anyone been able to use User Walls and/or Private Message with external users?
Welcome to the Q&A site for Question2Answer.
If you have a question about Q2A, please ask here, in English.
To report a bug, please create a new issue on Github or ask a question here with the bug tag.
If you just want to try Q2A, please use the demo site.