cdnjs is a free distributed JS library delivery service.
Fourthwall helps to create and launch a branded website.
Google Hosted Libraries is a stable, reliable, high-speed, globally available content distribution network for the most popular, open-source JavaScript libraries.
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.
Optimizely is an experimentation platform that helps developers build and run A/B tests on websites.