The relevant question is only whether the publishing journal is a "genuine" open-access journal. As a rule, such a journal will be listed on http://www.doaj.org/. It is of no importance through which additional websites the article is channeled.
Even if journals have not (yet) been registered with the DOAJ, publication fees can be covered through the publication fund. In all cases, journals must be genuine open-access journals, and according to the German Research Foundation's regulations, they must have strict quality-assurance procedures in place.
The critical factor is the invoice date. Funding is allowed only for fees invoiced during the current financial year. Please make sure that all invoices of 2018 are submitted to us by the end of January 2019. Applications which are submitted after 31st of January can not be considered for funding.
The financial year 2019 starts on 1st February 2019.