I have finally found how to insert music into the iphone 4 database, without using itunes. My son showed me a program from cydia called Mewseek,works on his jailbroken ipod touch running IOS 5.1.1, and on my jailbroken iphone 4, on IOS 5.01.
Please do not ask for help with jailbreaking in this thread, try the iphone dev team blog for that.

On to the howto:

1.Install Mewseek from cydia, preferably the unlimited version from the xsellize repository.
2. Plug your iphone/ipod touch into your computer running ubuntu (works on 11.10, and presumably above versions)
3.Using nautilus from the home folder icon, navigate to the devices downloads folder,copy the MP3 files here.
4. Run Mewseek on the idevice, click on the downloads tab, select all, then click Add to Ipod.

Works for me.

Now if the guys working on libgpod could just reverse engineer this little program to figure out how the hash value is computed...we could have native support for newer IOS devices in linux.