I'm not sure if this is covered already, but I added extra dictionaries translating to/from dutch based on the Babylon dictionaries (
http://www.babylon.com/free-dictionaries/).
I work on linux and had to install stardict-tools and of course marisa and penelope (as described often enough). The recipe is as follows:
stardict-editor #open stardict-editor
#An editor will be opened where you need to browse and select you .BGL file(Babylon Dictionary)
#In the bottom of the opened application you select BGL file and click on Build button
#It will create a file with an extension .babylon.
#Next browse and select this file
#In the bottom of the opened application you select Babylon file and click on Build button
#That's it. It will create 3 files (.dict.dz, .idx, .ifo) in the current directory
python ~/penelope/penelope.py -p <idx name without extension> -f <from> -t <to> --output-kobo
#Now the dicthtml-<from>-<to>.zip is created
#N.B. <from> and <to> are the 2-letter language abbreviations
#Next copy the zip file to .kobo/dict on your Kobo and translation is there.
#Unfortunately only lookup, not via search.