Drupal.org website (as well as the Drupal project and the community) is run primarily by volunteers.
It's built with Drupal 6 and has many customizations in code. There are many Drupal.org-specific projects that are used to organize improvements and code.
Who are the maintainers?
- Drupal.org infrastructure team leaders (org chart)
- List of Drupal.org webmasters
- The Drupal community as a whole maintains the content on Drupal.org