I just released version 2.3 Beta 19 with languages updates (Spanish and German mainly) and finally an additional feature that should help any contributor to translate the program and then propose to other users an easy way to install his translation file with just a double-click.

I'll create a translator's guide in the coming weeks that will give full details.
Meanwhile, you can already test this feature with the Traditional Chinese translation file created last year by Jarod Yang in this Feature Request. Download it, change its extension by sh3l (Sweet Home 3D language library) and double-click on it. This will launch Sweet Home 3D, copy the SH3L file in the languages subdirectory parallel to furniture one, and select immediately the language it contains in the user interface. How could you it be simpler? [;)]
Miserably, the file associations with a Java program is still buggy under Linux, and this may not work under this system. If it doesn't work, you'll have to copy the sh3l file to its destination folder by hand:
- under Windows, this folder is C:\Documents and Settings\user\Application Data\eTeks\Sweet Home 3D\languages,
- under Mac OS X, it's the subfolder Library/Application Support/eTeks/Sweet Home 3D/languages of your user folder,
- under Linux and other Unix, it's the subfolder .eteks/sweethome3d/languages of your user folder.

I'll probably add in a future version a + button beside the Language combo box of the Preferences pane to handle nicely this problem.

[April 10, 2010] I published today the translation guide . [:)]