It's AGPL. If you do not need any enterprise feature like SSO, you do not need to "call us", it's free. But if you fork it and re-expose it to users, you will need to make your fork open-source.

Our business model is that we are the only ones that can grant a commercial license because we hold the copyright and we provide plugins that only make sense at the enterprise scale such as SSO and exportable audit logs.

So in a sense, if you are an enterprise and need to pay us, what is the difference ? Well you can audit the code and experiment with it prior to deciding if you'd like to pursue with us, and not have to go through a salesy pitch to self-host and stress-test our orchestration runtime.