From the license: "The free version of Unity may not be licensed by a commercial entity with annual gross revenues (based on fiscal year) in excess of US$100,000, or by an educational, non-profit or government entity with an annual budget of over US$100,000."
My reading of that is that it is the total revenue of the company, no matter how small the Unity project might be.
I agree, the wording is total revenue, gross at that, of the company even before you start on a Unity project. But hey, it's their engine so they can license it however they think works best for them.
But I wonder how it works if a company with that much gross revenue hires a third-party that does not make that much revenue to create the content for them. I guess the rule would apply to the third-party.
My reading of that is that it is the total revenue of the company, no matter how small the Unity project might be.