The "Artist Donation" is a program that artists of Piano Society can apply to and grant the people downloading their music a chance to thank them for providing the recordings. While you of course still can download any recording from Piano Society for free, you can choose to pay a fee to the artists using the "Donate" button from their biographies. You will be able to choose the amount yourself.
The payment is made using PayPal (www.paypal.com), owned by eBay, which has become an Internet Standard and uses encryption and confidentiality of high level, making the payment secure and reliable.
If you rather want to support Piano Society as the platform for the artists, you can donate directly to the site from the following page:
For any question regarding the Arist Donation program, including artists who wishes to apply, send an email to the following email address: firstname.lastname@example.org