I won't answer for admin but I will say, my GUESS is, you can take screen shots. I would not suggest taking screen shots of the forum or other users. If you're just making a video and showing people how the website looks and how to use it, I can't see anything wrong with that.
If you're ever unsure about a particular place or way to advertise, it may be a good idea to submit a support ticket, relay that place and get the nod of approval before going forward. Most standard places to advertise, it is going to be ok.
Be sure to read thru the FAQ and yes terms. You cannot purchase referrals by offering any incentive or by going thru a place that offers incentives to purchase. You cannot post to news groups or spam your ref link in any way whatsoever.