Andreas and RJ, if you'll permit me to play mother and knock your heads together a bit ...
I can see points in both of your arguments about commercial or not commercial.
Simply by the domain name, WikiTree would tend to be thought of as a commercial site - that's what .com is usually used to designate. WikiTree is not a registered non-profit corporation, therefore does not qualify to use a .org name, and there is nothing preventing it from ever making any profit.
The fact that WikiTree is dedicated to being free, in the past, present, as well as future intent, could lead people to classify it as "non-commercial". If, however, some means is found for WikiTree to make a profit - for example, if the ads provided more income than needed to meet expenses (which is probably a very far out fantasy and hardly likely to ever happen) or if some means of generating income could be found that does not include charging people fees to be members, then it seems to me that "commercial" would be a fair description of WikiTree.
I really think that there is no essential disagreement here of what WikiTree is (and is not) - just a matter of semantics.