I can't currently see a way how it is possible. All I see is a "Sign in through Steam" button, and according to Steam's Terms of Service, you are not allowed to share a single account (as far as I am aware). Giving passwords is not allowed so you should not really want to log in for a friend. I believe the system is automatic, so it'd be nice if you would just be able to donate for someone else without having to manually get it checked or approved. I'm not sure what the current way of doing this is, but I just suggested it as it was not clear to me.

I can't currently see a way how it is possible. All I see is a "Sign in through Steam" button, and according to Steam's Terms of Service, you are not allowed to share a single account (as far as I am aware). Giving passwords is not allowed so you should not really want to log in for a friend. I believe the system is automatic, so it'd be nice if you would just be able to donate for someone else without having to manually get it checked or approved. I'm not sure what the current way of doing this is, but I just suggested it as it was not clear to me.