Is it possible to...

[RaggedDruid]

have both the Apple firmware and Rockbox on the same iPod? I want Rockbox (because of Doom, mostly) but I also like the feel of the Apple firmware.

Also, if I put Rockbox on my iPod, do I have to take all my music off? I don't keep my music on my computer (I just delete it after putting it on my iPod) and I don't want to re-download everything.

[Llorean]

Firstly, you should always keep a backup. iPods aren't the most reliable device ever.

But Rockbox dual boots, and no part of the installation process requires the removal of your music.

[Febs]

have both the Apple firmware and Rockbox on the same iPod? I want Rockbox (because of Doom, mostly) but I also like the feel of the Apple firmware.

Yes.

Also, if I put Rockbox on my iPod, do I have to take all my music off?

No.

[rockboxacdc]

ok to switch from rockbox to apple just restart your ipod ( hold the middle and menu button) and when the apple logo appears flick on the hold switch