Pepper&Carrot just received a "license update" affecting all artworks, translation, materials previously published as Attribution 3.0 Unported (CC BY 3.0) to the updated Attribution 4.0 International (CC BY 4.0)  .
Reasons and motivations:
- The Free Software Foundation document CC-BY 4.0 as compatible with GPL(s) licenses 
- Creative Commons 4.0 is designed to be more global  With the release of 4.0, we’re also introducing official translations of the CC licenses The 4.0 licenses are ready-to-use around the world, without porting."
- A quick table to compare 3.0 vs 4.0  reveals there is no big changes on the form, just more clarity.