These files are distributed under the Creative Commons 3.0 Attributions share-alike licence. The complete licence can be found here: https://creativecommons.org/licenses/by-sa/3.0/legalcode
In short, you can do what you like with these, as long as you let others do it as well. A better short introduction is found here: https://creativecommons.org/licenses/by-sa/3.0/