Hi, I'm thinking about adding a new feature to my site:
People who submit articles will get their adsense banners shown on the article they wrote.
Get it?

But I want to make sure that google wont ban me if I do this.
Is it allowed?

it's done here on the forum. I think Google is fine with it.

Meaning, code from their accounts?

According to Google TOS, one can place the code on any website, as long as that website doesn't violate the TOS. So - if your website is fine, putting their AdSense code on it is also fine.