Proof of Concept
I wrote a small c++ program that converts the dict database (de-en.txt, approx 9MB) into an apple xml file (much larger) and use Apple's scripts to convert these into an usable database (120MB!!!, but still very fast!).
It is by far not perfect, but works fine for me.
Obviously the formatting must be improved, and it will. Maybe I should convert the program into a .pl or .py script when I have more time. If you want a copy of the source (I won't provide the database because of its size) feel free to send me an email.
The sourcecode used to create the dictionary files can be downloaded here:
ding2osx.dmg (2007-11-19)
If you use the code, please drop me a line so I know whether it is worth providing and improving it.