If you ignore the rare ancient myth or two, there are two main kinds of werewolf:
Werewolves are occult in origin from the medieval years onward to the 19th century where the Werewolf is a beast of supernatural origin having either been a person who sold their soul or had a magic spell or curse cast on them. Not undead, but occult and definitely bestial and hungry. Like undead, silver will be needed to kill these kinds of werewolf and that may be the cause of confusion in anyone who links undead with werewolves.
In the 20th century the theme of infection is added. You were bitten by one and now you're screwed. Decidedly not undead.
Practical immunity to standard weapons and a special sensitivity to Silver only showed up in the 20th century and I think that the Silver thing is only related to the undead in that silver purifies Evil, and werewolves are occult.
tl;dr version: werewolves may require special weapons to kill (silver) but they are not undead, just hard to kill before they die of old age.