loads of publishers re-released old DOS games on Steam by just packaging them with DOSbox, which is the exact same thing tbh
worth reading up on what the license for the specific emulators you're looking at says about redistribution though, some of the DOSbox cases got into some minor controversy (and potentially could have opened themselves to legal liability) by not including the required GPL license documents etc
Nintendo's official party line used to be that even developing emulators without a license is copyright infringement but I'm pretty sure that that's been well established to be nonsense