WordPress Themes page Ratings and "Add your review" widget

When you check out the themes on wordpress.org/themes/, there is a great little widget in the sidebar with star ratings and “Add Your Review”.

Is that widget available to us mere mortals as a plugin? If so, what is it called, and is there a “free” version?

I’d love to find out, as it is functionality I’ve been trying to add to several of my sites for quite a while and found no affordable option.

Thanks.