Is an iPod considered to be a Transport?

I have the Wadia 170i Transport, which is an iPod doc. I think you got it right.

Yup it transports music from its drive and in the end to your speakers

I don't think there is a precise definition but it seems that when most people here refer to a transport they mean a device that picks up the digital signal from wherever it is stored and passes it along to another device, still as a digital signal, where the conversion from digital to analog takes place.

I looks as if the output of the Onkyo dock is analog, meaning the conversion is happening within the iPod or the dock but I doubt anyone would quibble much with your decision to call it a transport.

I thought it was going to be digital to the receiver, but I think you're right about it being analog. It's fine for what it'll be used for.

I'd consider it a source.