So I actually snuck a new version of Songbird for Mac OSX PPC up to the server about a month ago. The dmg includes both Songbird and some of the extensions, including a working version of the Shoutcast plugin. At times I've had some instability with this version, so as always be sure to backup your configuration inside ~/Library/Application Support/Songbird2. (This directory is from memory, since I've mothballed my PPC Mac for the moment.)
Songbird_1.10.0a_macosx-ppc.dmg
Give me some feedback, if you use it. I'll probably turn on the Mac once in a ...