[Trisquel-users] Is Paypal compatible with software freedom?

[leestrobel]

I'm a little unclear as to whether Paypal is compatible with the free  
software philosophy. It seems that both Trisquel and the FSF will accept  
Paypal for donations, although perhaps that is just out of pragmatism?

If it isn't ethical, why and are there any reasonable alternatives for online  
payments/shopping?