No, no category from dmoz, but site similarity based upon keyword (I assumed that google make it's own group of keyword and call that bunch of keyword a category) beside that I just got another comment about related and seo, i.e if your site shows some listing against related:yoursite.com than it's good because it means that google knows what your site is about
Did now quite get it, but I see some relavent sites and some non relavent sites in that list. so, hard to come to conclusion.