Thanks to Peter Lemenkov who pointed me to this Monkey’s Audio decoder implementation. It has four strong points: GPL, C, small and clean. Oh, it also takes less memory too.
The only drawback is that old APE files are not supported (but nothing can play them on PPC anyway without x86 emulator) so I’m eager see APE support in MPlayer, Xine, VLC (or maybe it’s there already?). Preferably via libavcodec 😉