I just posted this earlier on a different thread. It belongs here as well.
After Garageband was ported to the iPod Touch I checked the Apogee site and, upon seeing that the touch was added to the compatible devices, eagerly purchased one. Problem is that the status light would only get to blue with Garageband as well as any of the other aforementioned apps. Two days back and forth with Apogee and they tell me it's a software issue that will need to be addressed by Apple. So for the time being, the iPod Touch remains incompatible with Garageband. What a drag.
Apogee is correct here. I discovered an app that does work with the JAM on the iPod touch 4G. Griffin iTalk. Not exactly Garageband, but it shows it can work. Surely Apple can fix this so it will work. Hopefully sooner than later.