What you should do if the channel is not installed is to launch to the channels page in the channel store where the user can install it. Before you attempt to deep link to the channel you should check if the channel is installed or not by doing a lookup to the device via the ECP
http://<ip address>:8060/query/apps
if it is not there, then use launch command to go to the channel store (I *think* current firmware will accept the deep link param now and send you to the correct page in the channel if you select "go to channel" after selecting "Add Channel".)
Certain partners have forbidden 3rd party deep linking... well at least one partner, Netflix - so we won't publish a public channel that does this.
- Joel