Commons' Licensing policy requires contributions to be released under a "non-revocable" license. This means that the copyright holder cannot cancel the license and prevent people using the work under the terms of that license. Non-revocable licensing is to ensure that people using Commons content can rely on that license to use Commons content, and to make derivative works. A release of a work into the public domain by the copyright holder is also not revocable.
For example, many files on Commons are licensed under some form of Creative Commons (CC) license. Creative Commons has this to say on the subject:
CC licenses are not revocable. Once a work is published under a CC license, licensees may continue using the work according to the license terms for the duration of copyright protection. Notwithstanding, CC licenses do not prohibit licensors from ceasing distribution of their works at any time.
Publishing your work under any Creative Commons license does not affect your rights as copyright holder. You may still release the work under any other license and may also exploit the work commercially.
What is not license revocation
- Removing a license tag from a file description page does not revoke the relevant license.
- Deleting a work from Commons does not revoke its licenses. Anyone who has the work or gains access to it in future can continue to use it under the terms of those licenses.
- Creative Commons, Frequently Asked Questions, What if I change my mind?