I would like to use Cinemachine since its already in my unity registry, but I just wanted to make sure if thats allowed.

Yup! Falls under tools :)
Appreciate you clarifying :)

To clarify the rule (because I see how it can be misunderstood/misinterpreted): 
Unity tools is any non-asset that is available in the unity registry in package manager - so things like cinemachine, probuilder, etc all qualify.
Actual assets (such as the "ethan" model) aren't considered "tools" and couldn't be used without preapproval.

But definitely if there's any confusion, ask! :)