I almost sold my Kobo Glo because it seemed that it is not possible to download custom dictionary. I bought eReader because I wanted to improve my English grammar skills. My idea was to have at least two dictionaries: 1) ENG to my mother tongue (Czech) and 2) some comprehensive English monolingual dictionary. However as I discovered Kobo's internal EN-EN is quite poor unfortunately and there is no EN-Czech dictionary. I was pretty desperate - until I found this thread.
The first thing I tried was to convert a Shorter Oxford English Dictionary (SOED) to my Kobo. I found it on the web in Startdict format. So I installed the first time in my life a Python compiler and used AlPe's Penelope script. It worked on the first attempt. However later I discovered following annoying issue:
The SOED contains multiple definition of the same word with added number in brackets. For example: "know(1)" and "know(2)". So when I look for "knows" the closest match was "knowe". I have to manually type "know(" to show "know(1)" and "know(2)" translation.
So I converted SOED to CSV format using Penelope and I created C# console app which stripped the brackets and numbers from entries (from the first string before '\t' char). After that I converted CSV back to Kobo dictionary. It seems to work now! However maybe there is easier way? It would be nice if Penelope support that (maybe already does, I just I overlooked that – let me know). The final SOED has 23 MB size.
After that I also successfully ported ENG-Czech dictionary (Lingea Lexicon 2002). It was a bit more difficult because I had to convert it from original encoded format (.trd) to StarDict format, but I found public decoder (lingea-trd-decoder.py).
So right now when I click on any word in Kobo, the ENG-Czech dictionary shows me Czech translation and when I want to learn more English I click on “A-Z” button and to "Translation dictionary" to show SOED translation. I had to overwrite FR-EN translation dictionary because for unknown reason it is set as default translation dictionary. I'm not sure why and if is it possible to change that.
So now I have everything I wanted – very good EN-Czech dictionary and one of the best monolingual English dictionaries. I’m not sure if full version of OED is necessary, but after one day reading I found every word I was looking for. Btw: Does anybody ported full OED to Kobo?
Anyway thanks everybody in this forum for your work, especially AlPe for his Penelope script