Dear Rich staff used to work as a movie usher and we sure wish we hadn't given away all of the movie posters (or one-sheets, as our boss referred to them) from back then. Who knew? It's weird how long Woman of Straw (one of our fave posters) played at that theater -- almost as long as Never Too Late.
Right, you had a question. The use of the "prohibited" language by movie studios is so that they can claim that the posters are not sold; they are licensed. That distinction would exclude the posters from the first sale doctrine (we explain the principles, here) which would otherwise permit you to resell them. But we think that the movie studio's argument will be difficult to make, thanks to this case. (Here's an article with more details.) As the case indicates, these types of statements are not enough to create a license. Although the case deals with promotional CDs, the general rule is that a license can't be created (1) without some method of agreement by the recipient; and (2) without some means by which the studio can track and retrieve its posters.
But the posters were given away for free, not sold, so how can the first sale doctrine apply? Even though the word "sale" is used when referring to the first sale doctrine, as this case states, the doctrine applies "not only when a copy is first sold, but when a copy is given away or title is otherwise transferred without the accoutrements of a sale." So, based on our reading of the case, we think your activities are probably within the protective limits of the first sale doctrine.