GD Rating System Pro 3.3 now has more powerful rich snippets implementation that allows you to configure rich snippets by specific type. But, you are using MarketPress plugin that implements own rich snippets, and they don’t have a way to expand them with ratings. Search engines can use ratings only if they are part of the rich snippet that has some wider scope, you can’t have only ratings included with no context, it has to be a rating for a product, or for the article or something else.
I am investigating ways to hook into MarketPress and add ratings only into their rich snippet, and I hope to have something done about that in the next 3.4 version.