Today I got an E-Mail from nukson.com about their new site. They claim to get my E-Mail ID from github. Then, I visited the site and found it a copy of stackoverflow.
So my question is: Is this site is a part of stackexchange or who owns it?
Not, it's not a copy. As it seems some users/mods are copying questions (maybe even answers) from Stack Overflow to populate the site with content and/or to get better searchmachine rankings, but most of the questions seem genuine. Tim Post already notified the appropriate department of Stack Exchange and they're looking into it.
Partial whois output of the domain:
So no, not affiliated with Stack Exchange. They also run on a completely different system, despite that they removed all notices about the underlying engine, I'm 99% sure that they run on OSQA.