How to Download iTunes in Ubuntu
You can follow the above steps, but it's a path that is fraught with pain and half-working features. iTunes simply isn't going to work well in Wine (and therefore Ubuntu). This is doubtful to ever change.
You may want to ask yourself why you're doing this. Are you looking for something to play music? If so, Ubuntu ships with Banshee and Rhythmbox, both of which can manage your collection and play most file formats. Are you trying to play back songs purchased in iTunes store? In which case if they're older protected songs you'll need to break the DRM and violate the DMCA. Are you trying to sync your iPhone or iTouch? Well, then you may be in some serious trouble. Even with a virtual machine it only kinda works. Are you trying to sync an iPod? In that case, Banshee and Rhythmbox both can do it for you.
The only thing you need iTunes for is the Itunes Music Store, and newer iPhones / iPods; older devices have been supported by Rhythmbox, Banshee, and gPodder.
ITMS...that's not going to work anywhere Apple doesn't want it to--and that includes Ubuntu.
Ubuntu is awesome; I run it exclusively at home--but I don't have any unrealistic expectations that everything will 'just work'. Everything will just work if everyone involved wants it to.
If you have a newer iPod/iPhone, the only thing you can really do is complain to Apple; they're the ones that encrypted the iTunesDB.
I've read that iTunes will work completely if you use a different approach: Don't install it inside WINE, but instead use VirtualBox in Linux. VirtualBox lets you run MS Windows inside a window on your Linux, and then you can install iTunes on that (virtual) Windows installation.
I'll dig up some details and reply.