In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- It is permissible to pay by credit cards and through Paypal.
2- The percentage taken by Paypal is not usury because they don’t loan you money, but provide you a service.
In responding to your question, Dr. Hatem Al-Hajj, Dean of the College of Islamic Studies at Mishkah University and a member of the Permanent Fatwa Committee for the Assembly of Muslim Jurists in America (AMJA), states:
For the merchant or recipient of donations, you may accept the credit card transactions. The percentage taken by Paypal is not usury because they don’t loan you money, but provide you a service. Those fees are administrative fees.
Almighty Allah knows best.