I love your captcha plugin but I hate as hell the auto translation in the admin environment.
English is not my first language but I learned computing in English and simply I don't understand the translations. All my OS's and keyborads are in English only and I avoid as hell any localized programs or codes.
Of course I have deleted all the translations in the plugin folder but I wish to suggest you to add a link or button to change to a default English language at will. Better if English is used by default.