Yes you can use media from the Public Domain and you can also use media licensed under the "Creative Commons Attribution ShareAlike 2.5 License"
Here are some _link_s you can get this kind of footage from"
http://emol.org/movies/freemovielist.htmlhttp://www.stage6.comhttp://video.google.com/nara.htmlhttp://commons.wikimedia.org/wiki/Category:Videohttp://www.archive.org/details/movieshttp://imovies.blogspot.com/And in answering yr 2nd question, yes DJs and VJs will be judged in one overall category this year. Cut off date will be the 30th of March 2008