How to make a website like "Yahoo Answers"?

[daniellee]

... the typical type of ask and answer websites where many people can ask questions grouped under different categories and others can answer and get rewarded (usually a raise of scores)...

Is there any script for download like what you would do to build a blog (wordpress, etc.)?

Another example: answerbag.com

Thanks for your answer!

[skillipedia]

You should start implementing your concept from scratch and make it unique.
I created Q&A in my web site and though it is different from all other Q&A (users ask and answer from their own web site) I found out keywords such as Q&A, question and answer are very competitive

Best of luck