Tools for manual translation of Constants/Messages .properties files

I'm looking for some tools that could be used by human translators during the process of translating our GWT application into other languages.

Currently, we have the English version of .properties files containing constants and messages, and need create the files for other languages. This tool should be easy to use, so even non-IT-lover can master it.

Or, do y开发者_运维知识库ou suggest other method for translation of the texts?

• I heard the "community" approach becomes quite popular, by that I mean that one uploads his texts to some (?) forum, and the community there creates the translations into other language - but as I said, I don't know much about this
• Are there any online platforms for this purpose?
• any other ideas?

See my SO answer for VB 6 source code, speech text is in french want to translate to english. The same answer works if you replace the computer langauge "VB6" by "JavaScript".