Fastly is a cloud computing services provider. Fastly's cloud platform provides a content delivery network, Internet security services, load balancing, and video & streaming services.
GitHub Pages is a static site hosting service.
Mapbox GL JS is a JavaScript library that uses WebGL to render interactive maps from vector tiles and Mapbox styles.
Mapbox.js is a JavaScript library provided by Mapbox for working with interactive maps and geospatial data.
Varnish is a reverse caching proxy.