What is a Creative Commons license?
Answer
Creative Commons (CC) Licenses were designed to enhance copyright by offering more options to grant permission for use of copyrighted works. Although they are not the only kind of copyright license available, CC Licenses are globally recognized. Creators who choose to use a Creative Commons license can provide details for the resource’s use. People who want to reuse copyrighted works are easily able to identify what they can and can't do with the work.
Creative Commons licenses are as follows. The top three are ok to use at ACE without further permission.
Attribution (BY): Allow to copy, adapt, modify, share the work as long as the original creators are credited 
Attribution (BY) - Share Alike (SA): All rights as Attribution (BY) license and new creations have to be licensed under same terms as the original work. 
Attribution (BY) - No Derives (ND): Allow to copy, share but keep the work unchanged and in whole for any purposes.
CC Licenses that designate non-commercial are not necessarily off limits. For resources with these licenses, please submit a Copyright Permissions Request form.
Attribution (BY) - Non-commercial (NC): Allow to copy, adapt, modify, share the work for non-commercial purposes only.
Attribution (BY) - Non-commercial (NC) - Share Alike (SA): All rights as Attribution (BY)-Share Alike (SA) license but for non-commercial purposes only.
Attribution (BY) - Non-commercial (NC) - No Derives (ND): All rights as Attribution (BY) - No Derives (ND) license but for non-commercial purposes only.
You can find more information about licenses from the Creative Commons website.