@wimmme
http://wiki.maemo.org/Bluetooth_PAN This might help you. It is called Personal Area Network and should make you able to create a LAN between two devices. But I did not test it. If you are running fine with this you could give us a hint how you did it

Edit: I found a tutorial how to setup the network with ip configuration
http://talk.maemo.org/showthread.php?t=58570