Este artigo do blog explica como configurar o seu Mac para obter acesso somente leitura ao Ext2 e Ext3. Esta solução também funciona com o Ext4, conforme observado nos comentários do artigo.
Você precisará instalar OSXFuse e Fuse-ext2 .
Fuse-ext2 needs MacFuse to run, but this is no longer maintained and does not work on Lion. OSXFuse is the next generation MacFuse, but Fuse-ext2 is not meant to work with this. Fortunately OSXFuse includes “MacFUSE Compatibility Layer”. Just make sure to select this option when installing OSXFuse and you are good to go.