Open Licenses for sharing your work by Jonah McAllister-Erickson is licensed under CC BY 4.0
In the context of open licenses, a license is a legal instrument for a rights holder to permit a second party to do things that would otherwise infringe on the rights held. A waiver, by contrast, is a legal instrument for giving up one’s rights to a resource, so that infringement becomes a non-issue.
Only the copyright (or other intellectually property) holder can issue a license or a waiver.
Some licences are presented within larger contracts, and those contracts can place additional restrictions on the licensee and indeed the licensor. This means that contracts can take away rights one would normally have under copyright and may also have some effect on the license. For example a publication contract, that distributes the articles under a CC-BY license but restricts the right of first publication to that particular journal.
Creative Commons Zero (CC0) functions as both a waiver and a license. It is intended for dedicating works to the public domain by waiving all copyrights in the work. However, in jurisdictions were that is not allowed, it also functions as a irrevocable, royalty-free, and unconditional license for anyone to use the work for any purpose. Unlike all other Creative Commons Licenses it does not include an attribution requirement.
CC0 can be used to ensure that data can be freely used by others regardless of jurisdiction.
The Public Domain Mark is not a license or a waiver, it is intended to alert others that the work has been identified as being free of known restrictions under copyright law. Including any neighboring rights, like rights of publicity or moral rights.
This shouldn't be confused with the Unlicense public domain software license and waiver that uses an identical logo.
