It's a bit of a grey area since they don't have your password, but they are using your account, but mods only really care if you are doing something dodgy. Just don't be an asshole and you should be fine.
Also if your friend gets you banned, well that's too bad, you let them play.
Originally Posted by Clown
Well you are still giving out your password to someone that is not you.
No, they could just be using it when you already signed in.
<Faint> the rules have been stated quite clearly 3 times now from high staff