that's not very correct in principe...But why can not they protect their rights legally because I assume that as they create this animation or mod or what you want they are in their right to claim some compensation for their work??
Sorry for my english is not my native language. =)
modding is supposed to be free and a hobby. (that's the origin of modding )
sinze the creation of patreon, modding turned very very fast into a way to get money.
sims modders are a good exempl of this change. such as others like popular games modders from skyrims or others big games.
that's the difference between mods and dlcs ( wich sometime are also free, but most dlcs are pay ), a mod is a way to show the appreciation of a game by working on it to make it better or adding things you will like in it and original dev doesnt.
that's also why steam fail miserably when they tryed to implent pay-mods.
if a mod is made for money, then its not a mod and it should be accepted by the original dev and become an "official mods" (wich technically should stay free)