They're full-length and free. I play Family Feud all the time. Unfortunately when I looked earlier I didn't see Bayou Billy.
Some games I play all the time are Commando, Tecmo Super Bowl, Jaws, RC Pro AM, Ivan Stewart's Off Road Racing, Black Bass.....just to name a few.
Everything on that site is free. If you're having trouble I can help you here (although I will be gone all weekend). But this is how I did it:
Download any NES emulator. I have found the FCEU one for Windows worked best.
Create a folder to store all your zipped ROM's in. Go to the site and save all the games you want to that zipped folder.
Open your emulator. Go to config, then input. Set up the controller however you desire. You should only have to do this once, but I've known some that you have to reset your controls every time you open/close the emulator. Then click File, Open and your new "Nintendo Games" folder should open with all the available ROM's you downloaded.
Most cheat codes work as well! Up, down, up, down, left, right, left, right, b, a, start
Good luck....let me know how it goes.