I'm very much far away from having 20 people/2,000,000 USD but what happens to the license if you buy this and then reach that?
If you're currently nowhere near that kind of threshhold, don't sweat it - we won't be checking up on purchases down the line, you do not need to start tallying your earnings, you are just welcome to use the fonts forever.
All I can say is, if you remember us 10 years down the line when you're rich, a donation or just support of our other work will always be appreciated 😄