Internationalization support has been discussed during March 26th 2013 developer hangout.
We reach consensus: Official support for i18n will be disabled. A CMake option named Slicer_BUILD_I18N_SUPPORT will be added and the option won't be actively supported or tested.
Why? Supporting internationalization properly would require to test all ITK/VTK/Teem/.. readers and we don't have the funding or resources to support that effort. If it is something you are interested in, make sure to drop an email on the developer list. We will be happy to provide more information.
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