The Atheros scripts allow you to set up new network interfaces, as you've surmised. In your example, you are creating a new station (client) mode wifi interface, and adding it to bridge 0 (br0).
You can have multiple wlan interfaces, allowing for client mode, WDS, etc.. However, I never got the networking configured right. I was able to create a new wlan interface and connect two TEW-632BRPs with it (unencrypted and at minimum rate). However, something was wrong with the iptables or routing config -- or something. The LAN clients couldn't pass traffic through to the wifi interface, so I could only access the second router via the shell of the first. I never tracked down why.
A lot of people desire more robust wlan configuration capabilities. I had hoped someone would follow up on my work with some proper scripts to set up the network stack correctly.