From Meta, a Wikimedia project coordination wiki
Introduction to licenses, blah blah blah, secret base, blah blah blah, nuclear missile bomb, blah blah blah, counting on you, utmost importance, win, good luck.
Licensing options 
Free licenses 
Use Commons where possible 
- Free licenses accepted under the Wikimedia licensing policy should be uploaded to Wikimedia Commons where possible, rather than here, to simplify reuse on other projects and archiving.
CC-SA-compatible licenses 
- Licenses compatible with the our default license, Creative Commons Share-Alike, are preferred.
- This includes the CC-BY license and works released into the Public Domain.
Non-CC-SA-compatible licenses 
- Licenses not compatible with the default Creative Commons license should be dual-licensed under a compatible license where possible.
- Works with incompatible licenses can't be remixed with one another, limiting sharing and reuse.
Non-free licenses 
- Non-free image used in a Wikimedia Chapter annual report.
- Chapters are required to submit annual reports, and may at times need to include non-free images.
- Chapters are encouraged to submit free images instead whenever possible. Images using this license
- option are not to be used outside the annual report pages.
- Do not delete unless directed by the uploading Chapter or a Foundation employee, or if the media
- using this tag is being used only for non-Chapter-related purposes.
- Non-free image uploaded by Wikimedia Foundation employees for Foundation purposes.
- The Foundation, by virtue of owning the server, may at times have its own esoteric reasons for storing
- such images on Meta. The Foundation or the uploading employee takes responsibility to the storage of
- this image and its eventual deletion.
- Do not delete unless directed by a Foundation employee or the license tag was improperly added by
- a non-employee.
- Non-free logo used in a grant or other formal document which is archived on Meta
- Chapters, Wikimania bids, and other groups pursuing projects with sponsors and partners may have
- grants, proposals, or other project documents listing partners and their logos. These logos
- may not be available under a free license, and the project documents may be archived on Meta.
- Such logos are not to be used outside of documents relating to such a partnership. Project
- maintainers are encouraged to avoid using them where possible.
- Do not delete unless in cooperation with the project maintainer, or if the logo is being used
- only for non-project-related purposes.
Technical implementation 
- Create templates for a new license if one does not exist
- Add new license templates to Category:License templates
- Add appropriate lines to MediaWiki:Licenses. See Commons:MediaWiki:Licenses for appropriate use.