Jantje:
Cool. have you got references? Technical details on the how and the consequences?
I don't have any technical references, just making similar assumptions as you are based on the physical arrangement and pinouts. I would say there are a few levels of compatibility:
- Physical compatibility: works with boards that have the same basic shield connector positions
- Voltage compatibility: works with boards that have compatible voltages
- Communications compatibility: works with boards that have serial comm on pins 0 and 1
- Network sketch loading compatibility: works with boards that can load sketches via the six pin ICSP connector, and which have an appropriate avrdude profile programmed on the Linux board
For the Due, I would suspect it enjoys the first three types of compatibility, but not type #4, which is the one you are questioning. So it comes done to the definition of compatible: to be called compatible, does it have to meet all types, or is it compatible if it just meets several? I can make an argument for either definition.