I have a six channel mixer via PortAudio, if you want it. Just fill in the callback. The code I have should be portable by replacing the PortPLATFORM.c file (mine is Mac-Carbon). You can include the few files in the distro as it is under a BSD type license, so it matters not what you do with it, (unlike GPL/LGPL). Just stick the files in there and add it to your distro, rather than making people install a ton of crap. I had SFX and vorbis/ogg working on it at the time.