German journal managers can apply to the Deutsche Forschungsgemeinschaft (DFG) for funding for expenses arising from the creation, expansion, transformation and operation of scholarly electronic publications. Among other costs, the DFG can finance contributions to PKP software.

Detailed information about the funding program as well as DFG's other Open Access financing opportunities can be found here:

Program: http://www.dfg.de/forschungsfoerderung/formulare/download/12_17.pdf

Overview over all funding programs:
http://www.dfg.de/forschungsfoerderung/wissenschaftliche_infrastruktur/lis/programme_aktionslinien/index.html