Creative Commons Copyright - The "Open" in Open Textbooks
Creative Commons is a nonprofit corporation that has pioneered alternatives to standard copyright restrictions.
Watch this short video on "A Shared Culture" made by the folks at Creative Commons.
Creative Commons: Spectrum of Rights
Below is a cartoon describing the creative commons copyright permissions in more detail. As an open textbook adopter or advocate/trainer you don't have to know everything about these licenses but a general familiarity will help you understand how you may use the materials in the textbooks you are considering.
When compiling different media with different licenses together to make an open textbook, it is important to label your created work with the appropriate license. Read here for how to derive your open license when creating a new work with adapted open materials.
Other Expanded Copyright Permissions
Community College Open Textbook Collaborative works predominantly with Creative Commons copyright licenses. The following material is about other forms of copyright. One of the other organizations that has pioneered the concept of extended copyright permissions is GNU which began licensing open software in 1984. Later GNU expanded its licenses to cover manuals, textbooks and other materials.
If you explore open textbooks in depth, you are likely to find some that are covered by GNU rather than CC. The permissions of the CC-Attribution-ShareAlike license are similar to the Free Cultural protections articulated in the GNU Public License.
There are also many authors and publishers who have written up their own custom copyright agreements. As you come across these, read the use agreements carefully. Although understanding Creative Commons will acquaint you with the general issues of extended copyright, each agreement is likely to have subtle variations. Be sure you understand whether you have permission to modify material that is not licensed by Creative Commons and that you cite the author and publisher properly.
Using the COT site, see if you can find something for English Composition that can be modified by you and has also been peer-reviewed. (Hint: Review the Creative Commons abbreviations from the About Creative Commons Licenses)