SocialEngine - Socialengine PHP: Elevating Your Online Community Experience.
mooSocial - mooSocial is the best social network script to create a niche community or social site.
JomSocial - Open Source Social Networking Software. Award winning open source community software by JomSocial. This social networking software is widely used by many Joomla users.
Elgg - Opensource social network engine
Diaspora - The online social world where you are in control.
Open Social - Open Social is an out of the box solution for online communities based on Drupal 8.