WordPress is one of the largest open source projects in the world, with contributions from millions of people to the WordPress content management system and to the open source projects derived from it. WordPress itself is built from another open source blogging software, b2/cafelog. The open source nature of WordPress means that anyone is free to:
- Run WordPress for any purpose
- Study WordPress and change it however they want.
- Redistribute WordPress freely.
- Create modified version of WordPress, or software built upon it, and redistribute that software freely.
WordPress is released under the GNU General Public License version 2.0. As part of the GNU GPL terms, all software derived from GPL licensed software is required to inherit the GPL license. Other examples of open source software licenses include the MIT License, the Apache License and Creative Commons Zero license. All of the above are so-called GPL compatible licenses, which means that content released under them can be included in GPL software.
Other examples of prominent open source projects are the Apache HTTP Server, the Linux operating system, the Mozilla Firefox web browser, the VLC video player and the Blender 3D modelling software.