Unless the IDSA can provide legal precedence to their position that running in an emulated environment is a derived work, their statement simply has no merit. It could be challenged based on the factors listed under 17-107 for any particular case even if there was precedence establishing it as a derived work. I invite anybody from the IDSA to provide me reference to such a precedent. If you ran a game which had no such restriction under an emulator, but you were using an image of the original OS that had a license restriction, that would still be very questionable and easily challenged in court. On the other hand it's completely possible to reverse engineer an OS as well as the underlying hardware.
Emulators can serve many other purposes.
They can provide education of the original hardware and software used in a system. Notice that this is not specific to the original hardware required to run the program. The only requirement is that the resulting copy is used in conjunction with a machine and is used in no other manner. Here's the part where I make a lot of you unhappy. Face up to it, ROM sites are illegal.