Even on the hosted version (zPay.live), invoices are still generated directly from the creator's wallet. There is no intermediary involved in the transactions.
Even if I wanted to take a commission, I couldn't, this was the exact intention.
Discussion
Cherry On Top: Self-hosting zpay.live is entirely free.
It's so lightweight, you wouldn't even need a full server. You could deploy it on a serverless lambda function on AWS, Azure, or any other platform.
Even with 10k-20k users on your self-hosted version, you'd never break their free limits.