No! Use it any way you want. You should'nt bother with any attributions or alike.
Our features are available for everyone. When you register as a user, you will have online access to usage charts and invoices for you invoice department.
No. But we are using the API ourselves, so we'll always do our best.
Check out your dashboard, it has a nice graph. If you need exact numbers when using the API you can utilize the X-Rate headers that the API is using in responses.
Yes. We use Stripe as a payment provider. Your information is stored with them and will never touch our servers.
Yes. You can always download past invoices from your dashboard. We'll also mail them to you whenever you get charged.
Throw us an email at firstname.lastname@example.org.