CC+ denotes the combination of a CC official license (unmodified and verbatim) + another separate and independent agreement granting more permissions.
It is NOT a new or different license or any license at all, but a facilitation of more Permissions beyond ANY standard CC licenses. Worth emphasizing is that CC+ (and use of that mark) requires that the work be licensed under a standard CC license that provides a baseline set of permissions that have not been modified or customized but reproduces the license verbatim. The plus (+) signifies that all of those same permissions are granted, plus more.