Pressflow
Pressflow is a distribution of Drupal with integrated performance, scalability, availability, and testing enhancements.
Pressflow addresses a long-standing problem: High-traffic sites use stable versions of Drupal, and stable versions of Drupal are ineligible for enhancements to solve performance bottlenecks discovered after widespread deployment.
Like Drupal, Pressflow is free, open-source software released under the GNU General Public License, versions two and later, as published by the Free Software Foundation.
Like Ubuntu leverages Debian, Pressflow leverages the success of an existing popular open-source, free software package with enhancements targeting a specific user set. Releases of Pressflow correspond to Drupal core releases and maintain module and theme compatibility.
