If I go to the DNN Software home page then I get only very vague descriptions. So I went to the "Contact Us" page where they say:
"If you have questions, feedback, or just want to say "Hi," use the form on the right to tell us what you need. We promise a real human will get back to you quickly!"
I told them that if I either had (1) a bit more about what they do or (2) an idea of how much they cost then that would help determine whether I want to pursue it further. I have not heard from them.
After submitting that, I did find something that had a little bit more but not much more and I forget where it is. As best as I understand what it says, their definition of social is different from most people. It is intended for businesses to create a "social" feeling and to allow data from customers to be best used as a resource for the business. A critical issue I think is that (as I understand it) Evoq Social is not for social groups but instead it (as I understand) satisfies the needs of the business in a manner called "social". I think in this context social is used from the point of view of a business that uses social networking such as Facebook for commercial purposes but not for the primary purpose that Facebook members use it for. That might be an overly cynical view and/or inaccurate explanation of what it is but if not then I hope they correct me with a more accurate description.
I think I did read somewhere that Evoq is a complete rewrite of DNN, so yes Evoq is the same as DNN with improvements but it is my understanding that in reality all the code is new.
Another mystery is what the "Success Network" is. I did get a few responses when I sent a message asking about it but the responses were vague about what it is.