DIVE INTO LICENCES /
open content
http://www.opencontent.org
This licence is based on the GPL, but written to be more easily applicable to content other than software, in particular texts. The license grants the following freedoms:

a  to make exact copies and distribute those, as long as the license is distributed as well.
b  to modify a copy of the content, as long as the modifications are prominently noted and that the derived work as a whole is licensed under the same terms.

As always, there is no need to accept the licence, but only accepting the licence allows you to copy and modify the content.