[Markismus]

Hello CampfireEdition,

Penelope is here: https://github.com/pettarin/penelope

If you scroll down on the linked page you see what you must do to install and use.
It is most easily done in Linux, but you could install python on windows and run it from there.

The help states:

optional arguments:
  -h, --help            show this help message and exit
  -d, --debug           enable debug mode (default: False)
  -f LANGUAGE_FROM, --language-from LANGUAGE_FROM
                        from language (ISO 639-1 code)
  -i INPUT_FILE, --input-file INPUT_FILE
                        input file name prefix(es). Multiple prefixes must be
                        comma-separated.
  -j INPUT_FORMAT, --input-format INPUT_FORMAT
                        from format (values: bookeen|csv|kobo|stardict|xml)
  -k, --keep            keep temporary files (default: False)
  -o OUTPUT_FILE, --output-file OUTPUT_FILE
                        output file name
  -p OUTPUT_FORMAT, --output-format OUTPUT_FORMAT
                        to format (values:
                        bookeen|csv|epub|kobo|mobi|stardict|xml)

So to use it for bookeen, you take e.g. a stardict dictionary and convert it to bookeen:

python -m penelope -i stardict-dictionary-name -j stardict -f en -t ru -p bookeen -o bookeen-dictionary-name