As I did not answer to the list in the first place, I'll do it again.
It's there at l4/pkg/io
I used the svn checkout command provided at http://os.inf.tu-dresden.de/L4Re/download.html which apparently contains a restricted number of packages. I just saw much more packages were provided within the snapshot tarball.
You give it the cap to sigma0, but I won't go further, it's not supposed to be used by apps. Ned is the component that loads programs and sets up their initial environment, including caps. You cannot list them, but you do know them because they are specified in the loader script. Programs generally do not know anything about physical addresses or memory. The memory allocator provides you with memory in the form of dataspaces. Those dataspaces can be mapped into an address space. For device iomem io also provides a dataspace that gives you access to the mmio region of the devices the app is assigned to.
As my goal is to probably replace the standard io server implementation and to extend some kernel mechanics, I don't really want to base myself on L4re and its high level servers. I actuall want to understand and use the basic kernel mechanics. I would like to know how and where the sigma0 cap is granted to io and moe as well as some kernel interface / internal insights, if any documentation or example is available.
Thank you very much for those answers, the snapshot packages are already a good starting point for me.
François