Sure they are, because i believe you've missed the point by trying to think too simply.
The ordinance only requires AirBNB not charge service fees are people who are unlicensed.
Imagine, instead, LA requires licensing of people who download torrents (much like they are allowed to require that people register illegal weapons, etc, and then charge folks for it).
Then they say "ISP's can do whatever they want, but they can't charge subscriber fees to people who download torrents who have not registered. Doing so is a misdemeanor".
Like I said, you can literally change the words "hosts who have not registered to rent their home" to "people who have not registered to do X", where X is pretty much whatever you want.
(For the curious, here's what you have to do:
http://sf-planning.org/office-short-term-rental-registry-faq...)
The actual ordinance text:
(e) Criminal Penalties. Any Owner or Business Entity who rents a Residential Unit for Tourist or Transient Use in violation of this Chapter 41 A, or any Hosting Platform that provides a Booking Service for a Residential Unit to be used for Tourist or Transient Use in violation of the Hosting Platform's obligations under this Chapter 41A, shall be guilty of a misdemeanor.
Any person convicted of a misdemeanor hereunder shall be punishable by a fine of not more
than $1,000 or by imprisonment in the County Jail for a period of not more than six months, or
by both. Each Residential Unit rented for Tourist or Transient Use shall constitute a separate
offense.