Basically, emulators are legal (Sony v. Connectix). Pirate ROMs are not (the "24 hours" excuse is BS). Hopefully they don't provide, link to, or otherwise encourage the use of those. There are perfectly good public domain ROMs they can use for the demo.
IANAL, though, so if the person who made this gets any nastygrams, they should talk to someone who is.
You must have not even looked at the link, because these cannot possibly be mistaken for "public domain ROMS". And yes, he provides, links to, and encourages the use of.
I was only commenting on legality in general. Commenting on the legal issues of some specific person's circumstances is something that should be left to lawyers.