I believe copyright has to be signed away or sold--someone who isn't the original holder can't just post a notice and get it. At least, any writing "work for hire" contract I've ever signed has had a specific section for that.
If TORC did want the copyrights of everything posted on its boards, then everyone would have to agree to that on registration. I don't remember any more what was there in the boilerplate, but I think I would remember assigning the copyright of my own writing to them--it's the kind of thing I tend to notice. . . .
(One of my pieces of work for hire was a little "gift book" thing on unicorns that was in print for at least 10 years and sold, I'd guess, at least 100,000 copies. )
(Hasty edit to add, that sales figure is completely because of the subject matter and the nice little cover--the text I wrote had nothing to do with it; I just wish I had a nickel a book or something. . . .)