You can do it with FFMPEG outside of Wowza – just combine separate video and audio streams into one new stream for each language you want:
You may also be able to use FFMPEG to combine your video stream and multiple audio streams into one single MPEG-TS stream, then just select different audio tracks for playback with different “.stream” files in Wowza (as described in wifisolution’s second link above). I have not tried this method, though. Instructions for FFMPEG as Wowza MPEG-TS encoder here: