Strictly speaking, you are correct with your concern regarding opening additional ports could increase your security risk. You should only open ports that are necessary. But, on the flip side of that argument, just because a port is open does not mean something bad can slip into your network. If a port is open, there must be an application or service on the inside of your network that is using the port. It is the application or service that would have a weakness that might result in a security threat.
You don't hear about Microsoft or Linux or anyone releasing a patch for a port. Its always an application or operating system patch.
Now with that out of the way, Streamer has been running for about 4 years now and I don't ever recall a security related incident (knock on wood) Iain, KMeat feel free to chime in hear
You can tell ZoneAlarm to allow traffic on port 8466 for the Streamer application.