Though its GUI isn't as pretty, and the options are more limited, Darwin Streaming Server [10.1mb download] includes a broadcast server that seems to work great. Plus you don't have to drop a grand on OS X Server! I've got it working with little setup and am watching TV on my G3 via my G4's FireWire A/V IO box right now.Here is a direct download link.
Note: you must be running 10.2.8 or higher to use this software, and you'll need to login to Apple's Open Source site to use the above download link.

