I ran across this thread in my search today for the same thing... line art of the burning dude. I, too, was only able to find the PNG raster file. So... using it as a template, I redrew it in Illustrator. It isn't perfect â€“ I up-rezed it in Photoshop, used Photoshop to find the outline, exported that path to Illustrator and cleaned it up in Illustrator. All of which was done to save time instead of drawing it from scratch. No doubt took longer doing it that way, but it's done. The resulting PDF file, together with some text treatments, is at http://www.wetsystems.com/burningman/art/
. Please feel free to use anything you find in that directory.
Since I've not seen any copyright reference on the logo, my assumption is that it's in the public domain and free to use. If that isn't the case, please let me know and I'll pull it down immediately.