Just found this thread, sorry. To answer the questions:
* We are officially partnered with NBC. I setup the site and still completely own it. All of the contributions are made by fans (though we've had some of the cast and crew update their own information pages).
* Since it's not proofread by writers, there may be mistakes... however with so many eyes on it the hope is, like Wikipedia, that mistakes get caught more quickly and easily. It's not a canonical source, but it is indeed a good source.

* The definitions are likely to be close and in many cases correct, however they don't release concise information all the time that is documentable so we try to do the best we can with what we're given. Their goal is to make an entertaining show and our goal is consise documentation of it. Often the goals overlap, but sometimes they don't.
* NBC links to us on a number of their pages and even has direct links to some of our information portal pages at
http://www.nbc.com/Heroes/evolutions The portals are a neat graphical organization of the information. They're also currently including links in the Heroes Interactive sessions that accompany each new episode.
* They repointed the old NBC Heroes Wiki to heroeswiki.com, so all the old links should go to the right place now even if the link is still originally to NBC's old wiki.
* Heroes Evolutions is a broad term used to describe all of the content they're promoting outside of the show itself. So in a sense it could be considered part of Evolutions, though I personally don't call it part of Evolutions since all of the other material is written by the writers.