Is there any contact info in the readme? I would contact the person if possible to simply ask permission. Worst case is they say no.
I think it's likely from what they wrote that they were simply worried about someone taking their art and claiming it as their own (shoving it into their own art pack), rather than someone actually using it as intended as a game sprite (or they wouldn't have released it in such a format). This is coming from someone who has slapped together sprite packs and handed them out like candy. I simply ask for a credit somewhere, and I'm afraid I didn't bend over backwards researching the licenses when I made mine so I can imagine there might be a gap between their intention and strictest interpretation of their wording.
Of course, their intention may have also been to release the resources for use in non-commercial games only, so I would really just see if you could their permission directly.
And if it really is Micky Mouse, you have a bigger problem to worry about, as Frob pointed out.