Discourse is an open-source internet forum and mailing list management software application.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
Open Graph is a protocol that is used to integrate any web page into the social graph.
Phusion Passenger is a free web server and application server with support for Ruby, Python and Node.js.
Ubuntu is a free and open-source operating system on Linux for the enterprise server, desktop, cloud, and IoT.