It will be difficult for anyone to use this service because the code is on your server. You can replace the address with your own address or makes the QR code different to the displayed address. You can also change the amount on the invoice and "take a cut". You may not do it, but no business can trust you not ever doing it.
Alternatively, you can host the code on github and share it.
The code is super simple, you can actually edit the url I posted to change the content of the page ^^ there is no info stored in a DB anywhere. But you got a good point, theres no way for people to know that.