Information in the internet is susceptible of been copied anywhere, by anyone.
Except you have copyright rights of a book, a photo, or something like that, you can do NOTHING except the collegues told before: Complain about duplicity of the information to Google.
But think in the following: What is the "owner" of this information? You?
For example, when you post in a forum, nobody is the "owner" of this post.
You are the owner of a software license (because you have paid for it), the owner of a domain lease (because the same thing) or the owner of a hosting space in a server (the same reason) but you are not the owner of ANY information published in the internet, nor in a forum.
You are not the "owner" of your forum. A forum is a compilation of information published by hundreds, thousands users. Whitout these contributions, you had nothing.
So, if you see your forum is "cloned", please, think on what can be the reason of this "clonation", and try to do it better next time: Maybe you are not doing well with your staff, or even with your users.
Focus your mind in YOUR community, try to do it the best you can, and don't worry about others will do.
I'm sorry but it is my opinion.