1) Download Wolfenstein Enemy Territory 2.60-2.dmg from: ftp://ftp.ulyssis.org/games/et/download/mac/Wolfenstein%2520Enemy%2520Territory%25202.60-2.dmg
2) Run this file and install ET
3) Download the latest patch (2.60b): ftp://ftp.ulyssis.org/games/et/download/mac/et2.60bmac.zip
4) Install this patch (unzip it, you will see a directory macosx and copy the contents to your main ET directory)
5) Download the extra maps and etpro from: ftp://ftp.ulyssis.org/games/et/download/common/maps-etpro.zip
6) Unzip this file in your main et directory, it will at the latest (3.2.5) etpro and the maps used on Ulyssis.