All downloadable skins by http://www.made-by-kali.com is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
This means you can modify the files all you want, but you MUST link back to made-by-kali.com. If you choose to distribute the modified files, the link back must remain and your creation must be released under the same license.
Skins may be downloaded at the Main Site.