To be clear, I like Openrouter and recommend it to many people (I don't aim to "shit on it").
It does talk about a competing service, if I build a service that propose all the image gen models of Openrouter, and charge the user for it per token, am I allowed?
So yes obviously you can do what you want as long as you abide by terms of service, but the terms of service does NOT allow you to resell the API.