I assume you are looking for these files:
<variable name="bbebDictionaryRootFile" value="/opt1/dict/LIBRARY.MBF"/>
<variable name="bbebDictionaries" value="CDUS125D00001:STR_DICTIONARY_US:English-US,CDUS125D00002:STR_DICTIONARY_BRITISH:English-UK,CDUS125D00009:STR_DICTIONARY_EN_TO_FR:English-UK,CDUS125D0000A:STR_DICTIONARY_FR_TO_EN:French-France,CDUS125D00003:STR_DICTIONARY_EN_TO_GM:English-UK,CDUS125D00004:STR_DICTIONARY_GM_TO_EN:German-Germany,CDUS125D0000B:STR_DICTIONARY_EN_TO_SP:English-UK,CDUS125D0000C:STR_DICTIONARY_SP_TO_EN:Sapanish-Spain,CDUS125D00005:STR_DICTIONARY_EN_TO_IT:English-UK,CDUS125D00006:STR_DICTIONARY_IT_TO_EN:Italian-Italy,CDUS125D00007:STR_DICTIONARY_EN_TO_DT:English-UK,CDUS125D00008:STR_DICTIONARY_DT_TO_EN:Dutch-Netherlands"/>
<variable name="bbebDictionaryDefault" value="CDUS125D00001"/>
Info taken from kconfig.xml
Further I assume they will be in some kind of BBEB/LRF format, as there is a "FskBBeBDictionary.so" binary in the "\opt\sony\ebook\application" path.
The dictionary-files are not included in the "standard" cramfs-image, so they will be stored in some other part of the file-system and mounted in place.
You will have to "russify"
your reader to enable the test/autorun mode.
With a modified testscript you can get access to the filesystem and find and possibly copy out the dictionary files.
[Edit]As Unix-User you will also consider setting up a serial-console.
See Xaphiosis Post here
You should also have a look on the cramfs-tools
and igorsk fine deFSK-Scripts
Hope that gives you a start