Ah, come to France, maybe that explains my "sure of myself" answer in the parent comment. 0.0*01% + "à-valoir" is very common and cover the situation described here (eg you get paid a paid royalty, in advance, if the revenue ever exceed you are owed it, but if it's always under you never have to pay back).
Sort of a "I pay you 100€ but if this turns out to be a billion euro thing you get you gold ticket too".
Apparently, in this case, the license _did_ in fact forbid this usage, which is why they changed logo in the first place: https://en.wikipedia.org/wiki/Simon_Oxley#Twitter_Bird_Logo_...
No one wants to deal with a 0.0001% or 0.00001% royalty clause in an individual contact.
Ah, come to France, maybe that explains my "sure of myself" answer in the parent comment. 0.0*01% + "à-valoir" is very common and cover the situation described here (eg you get paid a paid royalty, in advance, if the revenue ever exceed you are owed it, but if it's always under you never have to pay back).
Sort of a "I pay you 100€ but if this turns out to be a billion euro thing you get you gold ticket too".
You can also be a generous person, and share a few pennies from your pocket.