### What license do themes need to have for distribution?

Could someone specify what license the themes need to have to get distributed in ikiwiki or Debian? The current included theme seem to be under the GPLv2. Does the [Creative Commons Attribution 3.0 Unported License](http://creativecommons.org/licenses/by/3.0/) also work. This way a lot of free CSS templates could be included, e. g. from [freecsstemplates.org](http://www.freecsstemplates.org/).