[zg94]

There's no mention of a fee similar to the infamous Runtime fee (which charged per install) here; instead, the closest thing on this page is a mention in the FAQs about how if the Unity runtime is included in a commercial product, then not only do you need permission from Unity to do so but you also will give Unity a fee that is roughly equivalent to 4% of the software's revenue.

This license appears to be intended for users using Unity to augment their business' operations; creating a commercial product with the runtime is treated as an edge case under this license.

[imtringued]

In a situation where the software is only used internally, it sounds like it would be very easy to game what "4% of software's revenue" means in both directions.

E.g. Unity argues that the entire production plant is the result of the software, therefore charges 4% on the revenue of the factory, meanwhile the customer argues that the software produces no revenue, because it is not being sold and therefore the bill is $0.

A fixed monthly fee solves this problem.