> 1) The purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes
> 2) The nature of the copyrighted work
> 3) The amount and substantiality of the portion used in relation to the copyrighted work as a whole
> 4) The effect of the use upon the potential market for or value of the copyrighted work
[emphasis from TFA]
HN always talks about derivative work and transformativeness, but never about these. The fourth one especially seems clear in its implications for models.
Regardless, it makes it seem much less clear cut than people here often say.