...OPolyglot is an excellent assistant for reading foreign documents, playing games, or working with unlocalized applications, all while keeping your data completely secure.
source code: https://github.com/fenenko/OPolyglot
The free and open-source rule-based machine translation platform
Apertium is a toolbox to build open-source shallow-transfer machine translation systems, especially suitable for related language pairs: it includes the engine, maintenance tools, and open linguistic data for several language pairs.