That and their high fees and lack of support on certain things make them even more unattractive. As such I would recommend Amazon Payments. They are not perfect, but at least ethically better than PayPal. Fees: volume-based pricing: 2.9% +$0.30 per transaction, or less; with no Addon fees.
This is a very useful project, but I feel it should have even more payment options (take a peek at how the Humble Indie Bundle does it for example).
In particular, having PayPal as the only USD provider can be messy. PayPal has a reputation for being a bully all the way back to 2010 - http://www.cnn.com/2010/US/12/04/wikileaks.pay.pal/index.html
That and their high fees and lack of support on certain things make them even more unattractive. As such I would recommend Amazon Payments. They are not perfect, but at least ethically better than PayPal. Fees: volume-based pricing: 2.9% +$0.30 per transaction, or less; with no Addon fees.
More info - https://payments.amazon.com/sdui/sdui/index.htm