DDE uses old Linux device drivers. It is not maintained.
We will probably replace most of DDE with rump.
While we still have dde, you can use the those drivers in GNU/Hurd userspace.
See Zheng Da's project page, as well as another guide.
Documentation
http://demo.tudos.org/dsweeper_tutorial.html
Why device drivers in user space; different possibilities for getting device drivers; DDE's origins and rationale.
http://wiki.tudos.org/DDE/DDEKit, http://os.inf.tu-dresden.de/pipermail/l4-hackers/2009/004291.html
Structural overview of the components.
Discussion
DDE essentially is a glue layer to embed Linux device drivers into another environement. In the DDE case, this other environment is a user-space task -- compared to the GNU Mach kernel having a in-kernel Linux 2.0 device drivers glue code (cf. paper by Goel et al.).