tedster - 5:14 am on May 13, 2012 (gmt 0)
You are welcome to advertise by buying links - always have been. Google just says those shouldn't pass PageRank. Google has been public about not liking sponsored Wordpress themes since 2007 - see [webmasterworld.com...]
In Google's mind, a paid link that passes PageRank is like an ad that doesn't identify itself as an ad. There are even US laws about that. And it's relatively common for free WP themes to sell embedded ad links to third parties and have those ads pass PR.
As I see it, the theme creator's link should be ignored if it's there. The value should be in publicity, not ranking power And if the theme creator sells advertising links to third parties within the theme that they distribute, those can be penalized if they pass PageRank.
I think Google's problem is that enforcement of this standard should have been uniform since 2007 - and they let it slide for too many years. They had some real public attention back then, especially when Matt M removed sponsored themes from the main WP site.