Correct – FLAC to WAV works very well on the slug, even serving more than one SoundBridge with different streams at the same time. As far as I know it is the closed-source status of WMAL which limits its availability on non-Windows platforms. If needed, dBpoweramp can be used to batch convert a library of WMAL files to FLAC while preserving tags.
FireFly Media ServerThe original FireFly Media Server