Yes, gtkpod merely communicates with the ipod device. This is accomplished despite the efforts
of Apple to block open-source users from using anything but their own software.
I received the iPod as a gift. I would have bought myself one of the open-source compatible ones
that uses lossless codecs. I'm not an audiophile and I just listen to the ipod while traveling to work-
I wouldn't build a home entertainment system around it.
I have used ripperX to convert some audio CDs to mp3 so I can put them on the ipod. I haven't
purchased songs from iTunes, Amazon or other sources. I heard there is something called iOpener
that allows windows users to use music they download from iTunes (as opposed to the file being
"locked" to a specific Apple device). I haven't used it so I can't comment.
I have downloaded podcasts and audiobooks and used gtkpod to load them on my iPod.
I found a resource for converting books on tape or books on CD to the format for transfer to iPod:http://blog.blazingangles.net/whatsthis/2007/09/creating-an-audiobook-on-linux.html