i believe it's something you're definitely allowed to see. ETS publishes a book of released exams. however, the book's been out of print for a while... and, honestly, the only way you can get a "feel" of the exam is to work through some (if not all) of these released questions. (i think that a well-prepared physics student who hasn't looked at the released questions can do at least in the 800's range, but if they bother understanding the sort of convoluted questions asked on the gre, they might do much better. also, there is also the worst case scenario where the student finds out that the exam is nothing like what s/he anticipated.)
i don't know the exact copyright details. but, i would have to say that on the grounds of fairness to all exam-takers (assuming they do not go through more shady means of unfairness), the brandeis released questions are definitely allowed.