I have implemented this for Fremantle in the apps I'm developing (the ones I created, not the ports) in the about dialog.
It has a button that will be opening a webpage where I'll explain:

• why you should donate some money or cookies

• why you should not donate some money (but cookies are always mandatory)

The webpage has a paypal button, and there the donor can donate the money that considers appropriate by means of paypal (if is registered) or with a credit card (if isn't registered in paypal).

It will be a nice experiment with zero cost.

I have to say I too have received some donations.