I don't think anyone needs to "host" the software. At least I didn't see a reference to it. (maybe I missed it.)
Related to all this is "slugging", an informal carpooling in Washington DC. There, it's drivenn (pun intended) by thick traffic and then need for 3 people in a car to use the carpool lane.
About Slugging
What's really interesting about it is that it seems to be something that naturally evolved as a response to traffic in the area. It has its own rules and etiquette.