You need some way to share your 3GS data with the the iPod
I'm not sure if the iPod Touch supports BT tethering as a guest. It was added to the iPad in 4.3.1, so I suspect that it may...
If it does, and you have the official Apple tethering on your 3GS, you can tether the 3GS to the iPod via Bluetooth. No JB required on either device. Once connected your iPod should treat the connection as a wifi network; allowing any wifi restricted app to run.
(BTW - my iPad is not with me right now, but I can verify this tonight)