Share-Alike on Your License

Creative Commons Attribution-ShareAlike 4.0

Mon, 01 Jan 0001 00:00:00 +0000

CC BY-SA 4.0 is the copyleft Creative Commons licence. Anyone may share, remix, adapt, and build on the material for any purpose, including commercial, provided they give appropriate credit and license their adaptations under the same licence or a CC-approved compatible licence.

It is the right choice for content that should stay in the commons even as it is remixed. Wikipedia uses CC BY-SA 4.0 in combination with the GNU Free Documentation License.

GNU Affero General Public License v3.0

Mon, 01 Jan 0001 00:00:00 +0000

AGPL-3.0 is a strong copyleft license with one critical addition over GPL-3.0: offering the software over a network counts as “distribution.” Anyone who modifies the software and makes it available as a network service must make the complete corresponding source code available to users who interact with it.

This closes the “SaaS loophole” present in GPL-3.0, where a company can run a modified copy on its servers without ever distributing binaries and thus never triggering the copyleft requirement.

GNU General Public License v3.0

Mon, 01 Jan 0001 00:00:00 +0000

GPL-3.0 is a strong copyleft license. Anyone who distributes the software, modified or not, must make the complete corresponding source available under GPL-3.0. It includes an explicit patent grant and patent-retaliation clause.

It also includes anti-tivoization provisions — you cannot distribute GPL-3.0 software on hardware that prevents users from installing modified versions.

Pick GPL-3.0 when you want to make sure derivative works stay open. Pick AGPL-3.0 if you also want to close the loophole where software offered as a network service is not considered “distributed”.