StarDict
Open Source
StarDict is a free GUI released under the GPL for accessing StarDict dictionary files.
dict.cc
Free
dict.cc is a free, multilingual online dictionary. The site's database can also be downloaded and used offline.
Apertium
Open Source
Apertium is a free/open-source rule-based machine translation platform.
Tagaini jisho
Open Source
Tagaini Jisho is a free, open-source Japanese dictionary and kanji lookup tool that is available for Windows, MacOS X and Linux.
Compare PROMT Translator with alternatives
Compare StarDict and PROMT Translator and decide which is most suitable for you.
Compare Apertium and PROMT Translator and decide which is most suitable for you.
Compare dict.cc and PROMT Translator and decide which is most suitable for you.
Compare Tagaini jisho and PROMT Translator and decide which is most suitable for you.