This page is an essay; it contains the advice and/or opinions of one or more Commons contributors.It is not a Commons policyorguideline, and editors are not obliged to follow it. Please update the page as needed, or discuss it on the talk page.
This page is an essay; it contains the advice and/or opinions of one or more Commons contributors.
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Эта страница вкратце: Multi-licensing means releasing content under multiple licenses. Doing so gives more freedom to users of the content, as they can choose which of the licenses best suits their needs. |
Multi-licensing means releasing content under multiple licenses. Doing so gives more freedom to users of the content, as they can choose which of the licenses best suits their needs. Multi-licensing with restrictive licenses may be desirable for compatibility with the licensing scheme of other projects; also, multi-licensing allows people who create derivative work to release that work under a restrictive license only, if they wish—that is, it gives creators of derivative works more freedom with regards to which license they may use for their work.
Many Commons users choose to dual-license their works under the GFDL and the CC-BY-SA license (all versions), using the copyright tags {{GFDL}} and {{Cc-by-sa-all}}. Both licenses have a ShareAlike 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.
