Fastly is a cloud computing services provider. Fastly's cloud platform provides a content delivery network, Internet security services, load balancing, and video & streaming services.
GitHub Pages is a static site hosting service.
jQuery is a JavaScript library which is a free, open-source software designed to simplify HTML DOM tree traversal and manipulation, as well as event handling, CSS animation, and Ajax.
Mailchimp is a marketing automation platform and email marketing service.
Semantic UI is a front-end development framework, powered by LESS and jQuery.
Twitter is a 'microblogging' system that allows you to send and receive short posts called tweets.
Varnish is a reverse caching proxy.