Does the free proof paperback copy of your manuscript interfere with getting published?

[Candise]

I've signed up for the NanoWrimo today and I noticed on their site that CreateSpace is offering winners a free proof copy of their manuscripts in paperback form. I understand how exciting it must be to build your own cover and to see your book in paper back, but I am also a bit concerned. Wouldn't this effect getting published? There is also the option of whether or not winners would like to make the book available to the public. But how can you send something out that has already been bound in paper back form? Do they also copywrite, because publisher can't buy work already under copywrite? Exactly what are we signing up for if we say "yes" to this deal?