Aether 1.5.12 is the last version of Aether to support Mac OS X 10.4 Tiger. However, the widely released build of 1.5.12 is not compatible with Tiger. A special Tiger compatible build is available here.

If you're already using Aether on Mac OS X 10.4 Tiger, you can update to the latest Tiger-compatible version simply by selecting "Check For Updates" from the Aether menu.

As always, if you have any questions, please feel free to email me.