A quick WhoIs search tells us that the site is registered by a "Four Seasons Tours and Travel" based in the Korea Town area of LA. My guess is that once you get on one of these shuttles they suddenly ask you for a "service fee" or something along those lines, or else they won't take you.
If you want to speak to them yourself, the phone number associated with the site admin is (213) 381 8000, which happens to also be the business phone number of Four Seasons Tours and Travel. Below is a link to their (very sketchy) Facebook page.
https://www.facebook.com/Four-Season...2850396160807/