Thank you for response.

1. I named it "Dogepay" because the "Stellarpay" has been used by someone. So I have to rename it and the word doge comes into my mind first. 😂
2. The private key will sign the transfer operation on the local by javascript. It will not send to the server or anywhere.
3. I'm working on a demo for Dogepay so the readme file will be committed later.