Apache is a free and open-source cross-platform web server software.
Bootstrap is a free and open-source CSS framework directed at responsive, mobile-first front-end web development. It contains CSS and JavaScript-based design templates for typography, forms, buttons, navigation, and other interface components.
Gravatar is a service for providing globally unique avatars.
Leaflet is the open-source JavaScript library for mobile-friendly interactive maps.
Open Graph is a protocol that is used to integrate any web page into the social graph.
Unpkg is a content delivery network for everything on npm.
WordPress is a free and open-source content management system written in PHP and paired with a MySQL or MariaDB database. Features include a plugin architecture and a template system.
Yoast SEO is a search engine optimisation plugin for WordPress and other platforms.