View source for Modifying the CC licenses

===CC policy===
CC recognizes that we cannot control or prohibit separate agreements or understandings outside of CC's standard license terms. After all, CC is not a party to the license – it is an agreement between the licensor and licensee. We can, however, insist that CC trademarks not be used in connection with separate agreements, understandings, and interpretations that create ambiguity and inconsistency with CC's standard license terms.

'''CC has the following guidelines for modifying or supplementing its licenses:'''

#'''If you make a change to the legal terms of any CC license, ''you may no longer call it a Creative Commons or CC license.'''''
#'''If you place an extra contractual restriction on use of the licensed work that has the effect of limiting or further conditioning the permissions granted to the public under the standard CC license, ''you may not use the CC trademarks (including the Creative Commons name) in connection with your license.''''' These extra contractual restrictions often appear in terms of use on websites where CC-licensed content is hosted, or as part of terms for downloading CC-licensed content.

::*Example of impermissible extra restriction: You may not impose terms of use that prohibit downloading the licensed work or terms of use that are designed to explain how the license works in a way that contradicts the plain meaning of the standard CC terms, such as dictating that the definition of NonCommercial hinges on the ''type of reuser'' as opposed to the ''type of use.''

:::::It is permissible, however, to have separate trademark guidelines that dictate how your logo or other trademark may be used in connection with the CC-licensed work. It is also permissible to impose website terms of use that restrict access to the website by minors pursuant to applicable law. 
::*Example of impermissible extra restriction: You may not impose terms of use that prohibit sharing of the CC-licensed work in certain formats.

::::: It is permissible, however, to distribute the work in a format that is not easily shared or to put content behind a paywall.
::*Example of impermissible extra restriction: You may not use website terms of use to impose attribution requirements that are more elaborate than those found in the standard CC terms.

:::::It is permissible, however, to impose terms of use that have the effect of increasing (or removing the conditions on) the permissions granted to the public under the standard terms, such as waiving the attribution condition or allowing translations of an ND-licensed work (see [http://wiki.creativecommons.org/CCPlus CC+])

CC does recognize that providing ''clarification,'' as opposed to modification, can make sense intuitively, and is arguably useful in a few limited circumstances, but only when doing so:
*is consistent with, and not contrary to, the terms of the CC license, and does not alter the usage permissions or alter the conditions imposed by the CC license
*does ''not'' require a particular class of users to contact the licensor in advance for permissions the CC license has already granted to all users
*does ''not'' otherwise increase transaction costs for any potential class of licensee

=== Rationale for the CC policy: ‘‘the beauty of standardization’’ ===
The above guidelines are designed to preserve the underlying principles and benefits of public licensing for licensors and licensees, by reducing conflicts and confusion that may ensue. One of the fundamental design principles of CC licensing is granting permission to the public in advance, thereby reducing transaction costs and facilitating reuse. CC licenses achieve this result through terms and conditions that are ‘’standard,’’ meaning the same terms and conditions apply for all content licensed under a particular CC license. The result is reduced friction for creators who want to allow certain reuses without negotiating and granting lots of individual permissions, and for reusers who want to make use the licensed content with minimal hassle.