Ask HN: Looking for a simple review website template

I'm looking to start a "review" website (think yelp). Is there any soft of open source software that is a template or a good starting place for this kind of site? I looked at phpBB but I think that misses the mark

"Hello, is there anyone out there who has implemented Yelp in its entirety and has made that source code freely available and consumable, with no cost or obligations at all?

The reason I ask is because I would like to start a competitor to Yelp, but I do not know how to implement or operate any of the services that Yelp implements and operates.

Thanks in advance!"