MoD256: My personel opinion doesn't change (and I think neither should banned for), but because this discussion, I have taken some investigation about unpermitted translations. Yes you are alright about that and advertising such isn't really a good thing and for legality issues I have deleted the links in my posts, but I call to mind that inside the GoG-Forum you can find a special "Multilingual GoGs" Thread which exists since Year 2010. There you can find pages of questionable legal/illegal content. And there I have posted a generally reference to the Patch Forum, because I can't decide which content or translation there is legal/illegal. Can you?
Legality issue is rather simple.
First post of the "Multilingual GOGs" -thread says that it's for fan translations. Now technically fan translations are a legally gray area. Technically copyright holder still holds the rights, but because most fan translators have strong anti-piracy attitude (you need to own the original copy to apply the language mod) and because the games aren't available in the target language copyright holders don't object the fan translations (it can generate more sales to them).
I haven't read the whole thread, so I don't know if there are links illegal hacks, which break the localization of GOG games and make available the official voice acting in languages which GOG doesn't support. These hacks are something which copyright holders object, because those reduce the sales of localized versions.