http://www.fileplanet.com/62226/60000/fileinfo/StarTopia-Language-Converter

i'm downloading the game at the moment, so i could not test if it is usable for the gog-version of ST.

It seems to work. You just have to copy the text files into the appropriate folder and change the startopia.ini (z.B. TextLanguage=German).

It works perfectly (with french language). Just do what Maiskolben said (with TextLanguage=French in my case).

Only for text. Useless until we get voices also.
I remember the so funny French dubbing :) especially Arona
i'll try to import frenches files from my french version (now not win 7/10 compatible).