The Creative Commons (CC) is a family of licenses with varying degrees of restriction on use. The license selector can help you determine which Creative Commons license to use for your work. Specific restrictions may be waived in writing if desired.
The possible licenses that are permissible on IMSLP:
The Creative Commons Zero license mimics the public domain but for copyrighted works. Specifically, the creator/copyright holder reserve no rights, not even the right to attribution (which is its main difference from CC BY).
The Creative Commons licenses use 4 types of restrictions:
Combinations produce the six licenses in increasing restrictiveness:
The Performance Restricted licenses are usually used when a composer uses a Performing Rights Organization (PRO) (e.g. ASCAP, BMI) to collect performance royalties. These licenses do not allow free live, broadcast or transmitted public performances, or recordings except as exempted under the copyright statutes of various countries. All performances, whether live, broadcasted or transmitted, are subject to payment of performance royalties to the PRO.
There are six Performance Restricted licenses, mirroring the six flavors of Creative Commons licenses. The only major difference between a Performance Restricted license and its Creative Commons counterpart is the performance restriction.
You can find the legal texts of the six Performance Restricted licenses on this page.
The Choral Public Domain Library (CPDL) License is used for files already licensed under this license. If you are selecting a license for a new work, one of the Creative Commons or Performance Restricted licenses is recommended over this license.