Mac
Project Zomboid works great on a Mac, but only when not running in a browser as far as I can tell.
Playing without browsers
Create a file called ProjectZomboid.command and put this in it:
#!/bin/bash DATA=$HOME/Library/Caches/Java/cache/lwjglcache/cloud.projectzomboid.com/ProjectZomboid; java -Xmx1024m -Djava.library.path=$DATA/natives -cp $DATA/zombie.jar:$DATA/lwjgl.jar:$DATA/lwjgl_util.jar zombie.GameWindow
Save it and open Terminal.app (In /Applications/Utilities). Type this and make sure you leave a space at the end:
chmod u+x
Then drag the ProjectZomboid.command file from the Finder in the Terminal window, which will paste the path to it, then press enter.
Now ProjectZomboid.command can be started by double-clicking on it in the Finder.
This has been verified to work in this environment:
zombiepie$ /usr/bin/sw_vers ProductName: Mac OS X ProductVersion: 10.6.7 BuildVersion: 10J869 zombiepie$ java -version java version "1.6.0_24" Java(TM) SE Runtime Environment (build 1.6.0_24-b07-334-10M3326) Java HotSpot(TM) 64-Bit Server VM (build 19.1-b02-334, mixed mode)