cdnjs is a free distributed JS library delivery service.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
MaxMind is a provider of geolocation and online fraud detection tools.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
OpenStreetMap is a free, editable map of the whole world that is being built by volunteers largely from scratch and released with an open-content license.
Pure CSS is a set of small, responsive CSS modules that can be used in web projects.