The free version has the custom translation feature now. (The updated paid version is still uploading.) There's a zip file with instructions and the txt files you'll need to translate inside. Basically, you extract two .txt files into the game's folder and translate them. The game will automatically use these two files as a text source. The game relies on line numbers, meaning removing or adding dialog lines is not possible.
Let me know if this works for you, or if you run into any problems. :)
