Open edX is an Open Source Web-based system for creating, delivering and an analysing online courses at massive scale.
Nate Aune (Appsembler)

Open edX is also:

• Open Source (AGPL licensed)
• A Python application using the Django framework

Open edX numbers (as of 2017):

• > 800 independent sites running Open exX
• > 5000 courses
• > 11 million learners at edX.org
• > 11 million learners at other Open edX sites

Minimum of two servers: one for apps, the other for databases (MySQL and MongoDB).

Cost estimate to run an Open edX site on 6 EC2 AWS instances: from USD 950 to USD 1400 per month (video snippet).

• Main Developer Portal
• Documentation Index
• Community Wiki
• Proposals Index

• The Anatomy of Open edX – Nate Aune, PyBay 2017 (video)
• Open edX 2017 Conference presentations list

• Slack
• Mailing list
• Code repositories:
  • Main codebase
  • Ansible playbooks
  • Local development

• https://alternativeto.net/software/open-edx/ (mostly alternatives to Open edX – the software)
• https://alternativeto.net/software/edx-platform/ (mostly alternatives to edX – the site)