[Plugin: Ad Injection] Can each author have their own adsense account?

Hi MyWPorg, each AdSense advert you insert is linked to an AdSense account. There is nothing stopping you from using AdSense from different accounts in each advert. You could set up custom adverts for each author using widgets quite easily. And it would technically be possible for the top/bottom/random ads – but only if you used custom PHP in the ad boxes to pick the correct adverts.

I’m not sure what you are asking about the sign up link – a sign up link for what? But there is nothing in the plugin relating to sign up links.