Any third-party software is never okay with Blizzard. It is possible to achieve, there would just pretty much have to be one host of that bot in the channel linked to w/e site. Users entering in a "code" into the channel have no reason to have the bot themselves, thus wouldn't need to install anything on their own computer.
This would require reversal of bnet 2.0 protocol though.
Another way to do what you want is to do what battle.net does themselves with their own website/forums, and have people sign-in through their actual battle.net account, thus verifying they are who they are.
But once again this requires bnet 2.0 reversal.
goodluck
