Watermarked would probably be a good idea. Though it is annoying for free users, it does serve the purpose of letting everyone who watches the video know what software was used to create it, and where to get it to try it out for themselves.

If you do add a watermark, I would suggest putting in in one of the corners, and making it slightly transparent, in order to reduce annoyance to the viewer.

You might put it in the corner, and stylize it so it looks like a TV Station logo (of course you would have your own branding and url). That might prove less annoying, then just a normal watermark.