the artwork can be commercial or whatever you want.
Not "whatever you want". In the quote, "it does not need to be free" means it does not have to respect all four freedoms that define free software. However, the FSF believes (well, at least rms believes) that the freedom to non-commercially redistribute exact copies must always hold. Whatever the kind of work that is distributed. That includes artistic works in video games. A license that prohibits such non-commercial sharing is unethical. It attacks the social solidarity of the community.
