About being licensed under the GPL ...
The psiKeds:client:server as whole is licensed under the GPL v.3.0: Whoever distributes a (modified) version of this component must also distribute the corresponding sources under the GPL v.3.0. But you are allowed to develop your own client (which then has not necessarily to be a derivative work of the original psiKeds:client:server)
... by the
- psiKeds licensing file: https://github.com/dtag-dbu/psikeds/blob/master/000-LICENSING
- GPL license file: https://github.com/dtag-dbu/psikeds/blob/master/000-LicenseAddons/licenses/license-gpl-3.0.txt
- original GPL license file: http://opensource.org/licenses/GPL-3.0