Well, why not an standalone application like RejZor's one?

Where can I subscribe ?

The standalone application could be only in English.
An easy option could be simply implemented, if needed (advanced users don't in my opinion) : if the standalone app is named "advavast.exe", it could search a file "advavast.lang", with a line for each expression/menu title/label text/option description (like the skype lang file

). If "advavast.lang" exists and is good formed (necessary txt file, possibly good number of lines and no empty lines) advavast use it, otherwise it will be in english...