Rocktopus by Kent Johnson is licensed under the Creative Commons - Attribution - Share Alike v4.0  International license 

http://creativecommons.org/licenses/by-sa/4.0/

Derived from:

* Sign of the Horns by dietz1, licensed under the GNU - GPL license.
* Bucket O' Octopi by yeoldebrian, licensed under the Creative Commons - Attribution - Share Alike v3.0 license.