cdnjs is a free distributed JS library delivery service.
Leaflet is the open-source JavaScript library for mobile-friendly interactive maps.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
Twitter is a 'microblogging' system that allows you to send and receive short posts called tweets.
Ubuntu is a free and open-source operating system on Linux for the enterprise server, desktop, cloud, and IoT.
Unpkg is a content delivery network for everything on npm.