Historic.Place as a part of OpenStreetmap is a free project. Nobody needs to pay for using the data.
The server infrastructure however produces costs which we cover by donations, exclusively.
You may donate as follows:
A bank transfer to the following account:
Kontoinhaber Contabo GmbH.
SWIFT (BIC) HYVEDEMMXXX
IBAN DE86 7002 0270 0661 9337 71
Kreditinstitut Hypo-Vereinsbank München
Betreff Kunde 15360