Minecraft – Is it possible to play Minecraft 0.30c multi-player using the Minecraft launcher

You need to download the multiplayer survival server. It can be found at https://minecraft.net/download at the bottom of the page.

The launcher supports passing a server address: see this update info post.

Minecraft <username> <password> <server:port>

<username> is the username you wish to log in as
<password> is your password. If this is set, the launcher will automatically start the game without waiting for you to press the button
<server:port> is an ip to a minecraft server. If this is set, the game will automatically connect to that server once the game has started.