iDisk is mac only, it runs only on mac os X, which only runs on Mac hardware.
Toshiba uses other types of hardware, hardware that mac os x doesn't support. Thus you can't install OS X (or any software that runs in OS X) on hardware it's not designed to run with.
Nautilus won't open the file because it's only usable on a mac.
iDisk's underlying core uses a file synchronization technology called "WebDAV", it's conceivable that you can use standard linux WebDAV tools to access your iDisk. More than this I cannot tell you, I don't own any other mac than a 5215cd performa nor do I own a dotMac account.
Hope that helps.
(oops, lol, didn't notice that this was such an old post, sorry for the bump)