What if I use a piece of software where I can place notes on a staff and have those notes play back with recorded samples of real instruments at whatever tempo I choose? Musician or programmer? I think it depends on how the listener hears the output. If they discern it as music, I am a musician.
More food for thought. Are home depot bucket street drummers musicians? It's a makeshift instrument for sure, but so are vocal chords.
The question was specifically about DJs so maybe I should comment on that. I think the guys who spin records and choose creative transitions between songs and also craft a set well are talented but probably fall just short of being musicians. In fact, "DJ" is a fine word instead. However, I do believe guys that do the scratchy scratch are getting closer like DJ Kilmore from Incubus or this dude:
http://www.youtube.com/user/djenferno?v=taNFcsnVF3Y