All themes are GPL v2 or later annd copyright their individual authors, and contributed by various people. 
Inidividual credits are given inside each .emerald file
(they are tar archives)

License:

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this package; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA

On Debian systems, the complete text of the GNU General
Public License can be found in `/usr/share/common-licenses/GPL'.