Apache is a free and open-source cross-platform web server software.
cdnjs is a free distributed JS library delivery service.
CentOS is a Linux distribution that provides a free, community-supported computing platform functionally compatible with its upstream source, Red Hat Enterprise Linux (RHEL).
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
JSDelivr is a free public CDN for open-source projects. It can serve web files directly from the npm registry and GitHub repositories without any configuration.
MathJax is a cross-browser JavaScript library that displays mathematical notation in web browsers, using MathML, LaTeX and ASCIIMathML markup.
Phusion Passenger is a free web server and application server with support for Ruby, Python and Node.js.
Ruby on Rails is a server-side web application framework written in Ruby under the MIT License.