When it comes to blocking porn, or any other domain, OpenDNS does not limit what it does to .com or .net domains. So long as the domain belongs to a category that you want to block, it will be blocked. However, since the categorization system is not automatic, rather it is user driven and relies on people tagging domains so that others can vote on them. This means that for some obscure domains they will never be categorized unless there is specific intervention (such as opening a support ticket with OpenDNS for a specific domain).
You can see if and how the domain for a specific website is categorized her https://community.opendns.com/domaintagging/
If you are concerned about a specific domain you can always add it to your blacklist. You can also just add the .ru domain to your blacklist, which will block all .ru domains on your network, whether they are porn or anything else
