Let me put this straight: It's perfectly ok to use Öffi for free. That said, donations are welcome. Hit the corresponding button on the left.

Donate via PayPal.
PayPal keeps around 50 cent for themselves. So if you can, use Bitcoin!
Send Bitcoins to my Bitcoin address.
You can use the popular Bitcoin Wallet app to receive and send Bitcoins.
Money transfer (SEPA):
Owner:Andreas Schildbach
Bank:Deutsche Kreditbank
IBAN:DE90 1203 0000 0001 8021 31