Commons:Multi-licensing

Multi-licensing means releasing the same content under more than one license. This gives reusers flexibility, since they can choose whichever license best fits their needs. It can also improve license compatibility with other projects that use different licenses. In addition, multi-licensing allows creators of derivative works to release their contributions under a more restrictive licence if they wish, giving them greater freedom in how they distribute their work.

Multi-licensing on Commons

Many Commons users choose to dual-license their works under the Commons:GNU Free Documentation License (GFDL) and the CC BY-SA license (all versions), using the copyright tags {{GFDL}} and {{Cc-by-sa-all}}. Both licenses have a Share-Alike (SA) restriction, ensuring the work will remain free no matter how it is used or modified. Using "all versions" of the CC BY-SA license maximises re-usability for sites which may be "stuck" with an earlier version of the CC BY-SA license.

Contributors to Wikimedia Commons can offer as many licenses for a file as they wish, as long as at least one of them meets the criteria for free licenses specified in the licensing policy. For example, files under a "non-commercial" license are OK only if they are at the same time also released under a free license that allows commercial use.

Copyright holders can release a file under additional licenses at any time, but cannot revoke licenses (Commons does not permit licenses which can be revoked - see License revocation). Commons tries to preserve mention on the file's file description page of all licenses that a file has been released under, as this can provide flexibility for re-users, and helps re-users show that they are respecting the relevant copyright.

Example

How multi-licensing under both {{Cc-by-sa-all}} (CC BY-SA) and {{Cc-by-nc-sa-2.0-dual}} (CC BY-NC-SA) can allow several images to be combined in a collage that otherwise could not be:

Licence (image 1, from Commons)	Licence (image 2, from another source)	Permissible licenses for collage	Explanation
CC BY-SA	CC BY-NC-SA	No license is permissible	The collage must be published under a licence which allows commercial usage (CC BY-SA) while at the same time it must be published under a licence which forbids commercial usage (CC BY-NC-SA). The collage is necessarily a copyright violation, since it can't satisfy both licenses at once.
CC BY-SA CC BY-NC-SA	CC BY-NC-SA	CC BY-NC-SA is permissible	Image 2 requires a non-commercial licence (CC BY-NC-SA) while image 1 allows both commercial and non-commercial licences. The collage creator must apply CC BY-NC-SA.
CC BY-SA	CC BY-SA CC BY-NC-SA	CC BY-SA is permissible	Image 1 requires a commercial licence (CC BY-SA) while image 2 allows both commercial and non-commercial licences. The collage creator must apply CC BY-SA.
CC BY-SA CC BY-NC-SA	CC BY-SA CC BY-NC-SA	CC BY-SA or CC BY-NC-SA (or both) is permissible	Both images allow both commercial and non-commercial licences - the collage creator can choose which to apply, or apply both.
CC BY-SA-2.0	CC BY-SA-3.0	CC BY-SA-3.0 is permissible	If different versions of the same Attribution-ShareAlike license are used for different images, the newer one must be used for any collage made from them.
CC BY-SA-1.0	CC BY-SA-3.0	No license is permissible	Version 1.0 of the Attribution-ShareAlike license is not compatible with later versions.

This shows how dual-licensing CC BY-SA + CC BY-NC-SA gives more freedom than just CC BY-SA, as well as various consequences of having different versions of CC licenses.

Wikimedia multi-licensing (2009 GFDL license migration)

• See Wikipedia:Image license migration.

See also

• Commons:Multi-license copyright tags - about how to deal with multiple licenses required for US and the source country and combine them with digitization copyright tags.
• {{Multi-license}} provides a heading to explain multi-licensing when applying multiple licenses to a file.
• Commons:License revocation - on revoking licenses