Question

Is this script is a clone to stackoverflow.com or stackoverflow.com using this script?

Answer 1

I think, this is just similar script. However stackoverflow is most know now q&a in many areas, but was not first. Here more other scripts like this.

Comments

Stackoverflow was first, q2a is similar but has one really important advantage for the most webmasters, it is based on php/mysql.
Besides q2a development is user driven, with each new version new features the users asked for are included. That makes it more flexible and goes far beyond a question and answers script.