KDE
KDE uses Free Software Foundation Europe's Fiduciary Licence Agreement which states in section 3.3:
FSFE shall only exercise the granted rights and licences in accordance with the principles of Free Software as defined by the Free Software Foundations. FSFE guarantees to use the rights and licences transferred in strict accordance with the regulations imposed by Free Software licences, including, but not limited to, the GNU General Public Licence (GPL) or the GNU Lesser General Public Licence (LGPL) respectively. In the event FSFE violates the principles of Free Software, all granted rights and licences shall automatically return to the Beneficiary and the licences granted hereunder shall be terminated and expire.
However, it is optional and every contributor is allowed not to assign his copyright to KDE e.V.
Read more about this topic: Contributor License Agreement, Users