Mac client/lack of

Hello, i'd really love to play this server and all, but I won't be able to unless there's a mac client. If there isn't one, just post it on this thread and block posts or something (and possibly make a client? ) but if the client is supposed to work on a mac, all i'm getting is this.

When I click play now, it like flashes and instantly goes back to that. Help pls?