At the time, you weren't allowed to hook arbitrary equipment up to the phone system -- everything had to be approved by AT&T. IIRC the hardware Woz used for his dial-a-joke setup was homebrew.
Apparently it was not homebrew; here are a couple articles saying that he rented the equipment from the phone company. So the dial-a-joke thing might have been entirely legit.
I'm guessing that when the article describes the dial-a-joke service as illegal, it's confusing it with his blue-box antics, which occurred around the same time. According to the following article (a fun read), the blue box preceded dial-a-joke; he got the inspiration for the service from a dial-a-joke line in New York that he called while demoing blue boxes to potential customers:
"illegal"?! I am not aware it would be illegal to run such a service at that time.
> the Macintosh was a radical innovation in its own right, being the first mass-produced computer to feature a "mouse" and a "desktop
Lisa? Star? Although that last one was not "mass-produced", at least it came out of a factory.