I'm sure rummaging around with WinSCP or similar SSH connection to a jailbroken iPod touch could transfer the music files back from it, but I treat music going onto it as a one-way street, rather like photos or anything else handled by iTunes, as it may well rename files etc using a proprietary standard meaningless to anything else. The files will still contain the tags with info about them so it will be possible to automatically get them back with 3rd party software, but that's a lot of unnecessary hassle.
If you didn't use the iTunes store to get the music originally, you're better off just getting it again from wherever you got it from originally.