It's definitely a business expense -- you have to pay the fees to keep your business on Etsy going, and the IRS lets you list fees as a deduction on your tax return.
However, I don't use Outright. Hopefully some Outright users can chime in.
I use Outright. I don't use Pay Pal though - I use a business credit card. But -- my Etsy Bill payment is a business expense, and it's categorized as "other expenses" for tax purposes.
I am not sure if it's matters which method of book keeping you are using: cash basis or accrual.