Drupal is Open Source
Drupal is open source software maintained and developed by a community of 630,000+ users and developers. It's distributed under the terms of the GNU General Public License (or "GPL"), which means anyone is free to download it and share it with others. This open development model means that people are constantly working to make sure Drupal is a cutting-edge platform that supports the latest technologies that the Web has to offer. The Drupal project's principles encourage modularity, standards, collaboration, ease-of-use, and more.
The passionate volunteer Drupal community is on hand to give support via various vibrant IRC channels, in the forums, and face to face at Drupal events. The community has also created Documentation for Drupal, which covers major topics related to working with Drupal. The worldwide community drives the innovation that makes Drupal the preferred choice for web developers and site owners. Everybody can get involved and make a difference to Drupal.
Dries Buytaert began the Drupal software as an message board in 1999. Within a year or so, more people became interested using and contributing to Drupal, so the project was made open source. Drupal.org came online in 2001, and the Drupal community gained momentum in 2005 with several code sprints and conferences. Read more about the full history of Drupal and Druplicon.
As well as the community, there are many dedicated companies in the Marketplace to help with your Drupal project. Providing expertise and a deeper understanding, they can help with design, development, hosting, spam blocking, theming, training, and more.