Veil is a modded caddy fork which gives API paywalls as a built in feature to the caddy webserver running in a reverse proxy mode. Veil aims to be a self hostable solution for those who want lesser number of features or want to tweak it as per yours wishes with a fully featured SaaS marketplace coming soon to ease your deployments and paywall management.
Below is a small demo for Veil.
Please refer to Veil docs to know more about the project.