hello Markus,
Let's go by parts:
About the CAN_CAN_EXAMPLE1, I would say don't worry.It is a generic CAN example project for SAM3X-EK board. This same sample was included with the latest ASF of Atmel Studio 6 and in the ASF standalone zip package (GCC & IAR). I decided to use it because I already have the kit board.
As I stated in my scope:
For this, will be required to add some services/drivers/components from the ASF using ASF Wizard (By cross checking with the existing CAN_CAN_Example1 project for SAM3X-EK).
I said some because that's what we need, just few libraries like can.h stdio.h, sysclk.h etc.These libraries were built by Atmel for the SAM3X platform, not for AS6.
About the github files, I haven't uploaded anything yet. I still running tests. And I agreed like the shield. Necessarily, a shield containing (among other things) similar transceivers should be considered for the Arduino Due. Which ones? I don't know yet but we'll find out soon. regards.