GNU General Public License (GPLv3 - for software)

The foundations (or ‘freedoms’) of the GPLv3 licence are the ability to:

• use the licensed software for any purpose,
• change the licensed software to suit your needs,
• share the licensed software with others, and
• share the changes you make.

Releasing software as a free work under the GNU GPL means that it will stay that way, no matter who changes or distributes the program. This is known as ‘copyleft’ - the software is copyrighted, but instead of using those rights to restrict users (as with proprietary works), the GPL ensures that users have the freedoms noted above. Learn more

GPLv3 is compatible with the Creative Commons Attribution Share-Alike (BY-SA) 4.0 licence - only this specific licence and version, and the compatibility is one way. CC BY-SA 4.0-licensed materials can be added to GPLv3 projects, but Creative Commons licensing is not suitable for software. Other considerations may also apply. For more on Creative Commons, see the information in the section above.

Pros

• Free licence that is useful for when you want to ensure your code stays open source.
• If you are planning to release your work under the GPLv3, you can easily build on, incorporate, or otherwise adapt other software/code released under the same licence into your project without issue.

Cons

• Generally not considered friendly to later commercial use as the licensing means the code remains open source.
• Considered a 'viral' licence due to how it applies to derivative works. GPLv3 requires your entire output to be released under the same licence if you have incorporated any existing code with GPLv3 licensing (e.g., you find a GPLv3-licensed project on GitHub, and insert some code from it into your own project. Your entire work now needs to be licensed under GPLv3 to meet the requirements of the licensing on that code you've copied).