Craigslist Forum System Clone

We want a very close replica of craigslist's pets discussion forum where all discussions and topics are occuring at the same time in real time.? ? Please? look over craigslist's discussion forum in detail including user registration and flagging and searching of content.? This is basically an exact? clone and needs to include? all of the functionality. ? We also need an admin to be able to manage/delete conversation, view flagged discussions, and block/delete users from using the forum.? If you have developed something like this before, please include a link so that I can try it out. This MUST be built on MySQL. I am open to the programming language, though. ColdFusion and PHP are preferred, but I am open to ASP etc.