Is it aganst adsense rules to have two adsense codes on one site under two diffrent id's is what i would like to ask?
Rubbish. You can't have 2 different publisher's AdSense code on the same page at the same time. You can however have different adsense code on different pages, or alternate between adsense codes on one page.
So i take it its allowed ? or best to ask google about it ? I will have the top half of the google adds on the site where the other person will have the bottom adsense adds , on a VB forum.
You can have multiple pub-IDs on the same page as long as the maximum number of ad formats isn't exceeded. I wouldn't do it personally because it could lead to disputes over how to share the revenue - also if one publisher gets in trouble with AdSense the others may be guilty by association.
https://www.google.com/adsense/localized-terms Why do people say things are ok or allowed without even checking the TOS?
Interesting, you learn something new every day. I still know a lot of people do display multiple pub-IDs on the same page and I don't know anyone who has got into trouble over it.