Download Link 
Form this post on the forum
Anyone still having problems with sound can try my newly minted plug-in. Very little testing but seems stable for me at least. HDMI output only atm (will provide option soon). To install download the file above and
sudo cp so.vm-sound-RPI /usr/lib/squeak/4.4.7-2357/
sudo nano /usr/bin/scratch
~ line 99, change... VMOPTIONS="$VMOPTIONS -vm-sound-alsa" to VMOPTIONS="$VMOPTIONS -vm-sound-RPI"
save, exit, run Scratch. Have fun!
Note: Plug-in only plays sound, no recording yet.