Apache is a free and open-source cross-platform web server software.
cdnjs is a free distributed JS library delivery service.
D3.js is a JavaScript library for producing dynamic, interactive data visualisations in web browsers.
Google Analytics is a free web analytics service that tracks and reports website traffic.
Google Sign-In is a secure authentication system that reduces the burden of login for users, by enabling them to sign in with their Google account.
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.