FOSS
FOSS means free and open-source software: public source code under a license that lets anyone use, change and share it. Drupal is FOSS under the GPL.
FOSS stands for free and open-source software: software whose source code is public and whose license lets anyone run it, study it, change it and share it. Drupal is FOSS. Drupal core is released under the GNU General Public License, version 2 or later, so you can use it for any purpose without paying a license fee.
Free software and open source
The two words come from two traditions, and FOSS joins them.
- Free software. The GNU Project defines four freedoms: to run the program for any purpose, to study and change it (which requires the source code), to redistribute copies, and to distribute your modified versions. Free here means liberty, not price.
- Open source. The Open Source Initiative publishes the Open Source Definition, ten criteria a license must meet. They include free redistribution, available source code, permission for derived works, and no discrimination against persons, groups or fields of endeavor.
How FOSS works in Drupal
Drupal.org describes Drupal as open source software distributed under the GNU General Public License, version 2 or later. Several rules follow from that, all stated in the Drupal.org licensing FAQ.
- Modules and themes build on Drupal, so they fall under the same license when you distribute them. Anything committed to a Drupal.org Git repository must be GPL version 2 or later and include its editable source.
- Contributors keep the copyright on their own code and agree to license it under Drupal's license.
- You may sell Drupal, but what you distribute must remain GPL version 2 or later, so your buyers can modify and share it too.
- Code you use only inside your own organization does not need to be distributed to anyone.
- Visiting a website that runs Drupal is not distribution, so a site owner does not have to hand its code to visitors.
Example
An agency writes a custom module for one client and delivers the finished site. Under the FAQ, an agency acting for a client is not distributing code in the GPL sense, so the module can stay private. If the agency later publishes the same module on Drupal.org so that other sites can use it, the module must carry a GPL version 2 or later license.
Common mistakes
- Reading free as no cost. The software has no license fee, but hosting, design, development and maintenance are still work someone pays for.
- Thinking custom code must be public. The GPL concerns distribution, not use. A private site can keep its custom code private.
- Mixing up the code license and the name. Drupal.org states that Drupal is a registered trademark of Dries Buytaert, which is a separate matter from the code license.
- Treating every contributed project as the same. Projects hosted on Drupal.org follow its licensing rule, but check the license of anything you pull in from elsewhere before you ship it.
For marketing and content teams
FOSS changes the buying conversation. You do not pay a license fee for Drupal core, and anyone may download, study and change the code. Budget for what the fee would not cover: core updates, contributed modules you rely on, hosting and the people who maintain the site.