AddThis is a social bookmarking service that can be integrated into a website with the use of a web widget.
Apache is a free and open-source cross-platform web server software.
Open Graph is a protocol that is used to integrate any web page into the social graph.
RequireJS is a JavaScript library and file loader which manages the dependencies between JavaScript files and in modular programming.
Twitter is a 'microblogging' system that allows you to send and receive short posts called tweets.