iPOD-os?

Are you talking about iTunes? Steve is not going to give you the OS for iPod

For iTunes go to www.apple.com and download.

If you are talking about Linux operating systems that can be installed on the iPod, you can find one for the iPod Nano here.

Seek Google's help to find out more.

yea there is one called "ROCKBOX linux" .. google it..

Here's a link to ipod linux *www.ipodlinux.org/Main_Page if you were talking about that.

the sound does not depen on which firmware u use .... there are 2 or 3 firmwares available ....

1. rockbox
2. linux

@pathiks rockbox and linux are 2 different firmwares for the ipod

aww sorry mavji my mistake..

Rockbox is open source firmware replacement under GPL but definitely not linux.
BTW, which one is better? Any idea anyone? Has anyone here used either?

well i did a lot of search on this .... and found tht ... rockbox has a huge db of themes tht really lets u customize ur ipod and linux enables u to play a lot of games .... which i dont remmbr as of now

Yeah I saw the site of both. Rockbox has huge range of themes but I somehow personally liked the linux themes more. Looks like rockbox lets you play lots of games too *download.rockbox.org/manual/rockbox-ipodcolor/rockbox-buildch8.html#x11-1030008

Any idea on battery life using each firmware?

i like it as it is.
I tried Rockbox. it is good