The version on GOG comes with this:
Dubs: English, German, French
Subs: English, German, Spanish, French, Italian
You can set these by going into the options when you open the launcher.
You can download the following dubs from here: English, German, French, Italian,
Polish, Spanish
http://en.thewitcher.com/support/#q29 I do not know whether they also include subtitles, but I think they do.
As for the Russian language pack, that's Steam only I guess. It would be awesome if all possible language packs were available through GOG though.