I don't mean to be rude here, but this is a completely free service - surely it's more or less a given that in exchange for a pretty excellent range of freebies, you have a link in your listings?
Someone more knowledgeable will tell you for sure, but I think those links are automatically inserted when you use one of the templates. If you don't want the links, you'll have to use another service, or make your own templates - that's my understanding of it anyway.
The other two links are to Auctiva itself, not to your Auctiva store - so this shouldn't confuse your customers. It just lets them see where you got your great templates