They are different models altogether, even that they look very similar. The one without the camera is the iPod touch 2nd generation from 2008, and the one with the camera is the iPod touch 4th gen from 2010. The 2nd gen has a Samsung CPU (same as iPhone 3G) so it only got up to iOS 4, 4th gen has an A4 processor so it got up to iOS 6. You may also be able to notice that the 4th gen has Retina display, the 2nd gen does not.