Scrolling text box in Keynote.app? Can I place a scrolling text box on a slide in Keynote? 

By default, the "Text" items do not scroll. Any added text that flows beyond the edge of the slide is hidden (truncated).
That seems to be possible, at least if you can accept it to be "animated", and scroll on command: https://www.youtube.com/watch?v=HHl72gfDl94