That iPhone Dev team has decided to port the linux kernel and BusyBoxto the iPhone and write a completely new boot loader to support dual booting.

iPhone Linux Demonstration Video from planetbeing on Vimeo.

I’m not sure that it really means anything for everyday users of the iPhone at this point, but it’s certainly interesting for geeks, hobbyists, code hackers and possibly developers.
If I had a spare iPhone I might give it a whirl just to see it work, but since I don’t I’ll just be satisfied with the announcement.
Any way you look at it’s pretty nifty.