GitHub App accepting payment outside of the GitHub Marketplace?

My understanding is that it’s “OK” to accept payment outside of the GitHub Marketplace (e.g. via Stripe). Looking over the following pages:

Billing Customers
Receiving Payment for App Purchases
Marketplace Developer Agreement

…Indeed I can’t find anything that says we are not allowed to do so. And to be fair, I’ve used apps in the past that accepted payment outside of the Marketplace ecosystem (PullReminders is the first that comes to mind, before they were acquired by GitHub).

I’m primarily interested in this because the current Marketplace requirement is 100 customers to become verified and allowed to accept payment. I’ve built an app that is specifically focused on GitHub Organizations, and so signing up 100 organizations is not only significantly more challenging, it would also mean I’d have to support 100+ organizations worth of data in real time, which could be immense, all while not yet earning any income. That’s a big ask on GitHub’s behalf. In addition, I’ve seen reports of others on here taking many months to get their app verified once they met the requirement. That doesn’t sound appealing at all.

So, just to be clear, is there nothing preventing me from implementing Stripe’s API and accepting billing via an external mechanism? My intent would be to roll my own payments, allow users to install and sign up for free via the Marketplace App, and then once in and using the app, they’d have the option to pay and move beyond the free tier that is offered by default.

That’s OK to do?