Apache is a free and open-source cross-platform web server software.
Drupal Multisite enables separate, independent sites to be served from a single codebase.
Drupal is a free and open-source web content management framework.
Open Graph is a protocol that is used to integrate any web page into the social graph.
ShareThis provides free engagement and growth tools (e.g., share buttons, follow buttons, and reaction buttons) for site owners.
Twitter is a 'microblogging' system that allows you to send and receive short posts called tweets.