A: The method for playing these games was never patented and even if it had been, such a patent would have expired long ago, so the method of playing a Mafia/Werewolf game is in the public domain. Artwork, trade names, and the specific wording of rules may be copyrightable, but if you are creating your own art and such you should be free to do so.
Mafia was indeed created in the 80s in Russia. I learned it in 1997 when my friend Andrew Plotkin came back from a crossword puzzle convention where they were playing Mafia. He thought a better theme would be werewolves and he created the basic roles of Werewolf, Villager, and Seer. I believe he has explicitly placed his contributions into public domain.
Our group hammered out the script, voting procedures, and other details that appear in Are You A Werewolf?, which other groups and companies have since added to. Many new characters have been added, but not by us, so I can’t tell you who came up with any of the other characters.
If you haven’t yet, you should certainly read Andrew Plotkin’s page on the subject.