CMS Drupal is developed and maintained through a community – users and developers. Thanks to GPL license (General Public License) everyone can get a free download and then use and support the development of that platform.
CMS Drupal is available on GPL license that enables a free download, installation and modification to suit your own needs. You can therefore save money on initial licensing payments, and the savings can then be invested in developing the very application. Similarly with modules available for Drupal and graphical skins, all you need to do is download them and install to your web pages. It is also worth underlining that Drupal is developed and supported by an enormous community of passionate people, fascinated with the idea of free software.
Drupal has achieved an enormous advantage over its competition not only because it has incredible capabilities but also because it is distributed as an Open Source.