On a Mac or Linux machine that is configured for running CT3 experiments (Java and Ant, etc., are properly set up), download the two attached scripts.
Download the scripts to your desktop.
Open a terminal window, and run
cd ~/Desktop; chmod u+x ct3*.command
Running ./ct3-checkout.command will do a Subversion checkout of the full CT3 source tree, into a directory called ct3repos in your user folder (~/ct3repos).
Running ./ct3-update.command will update the full source tree from Subversion, and then run the Ant build scripts for the trunk and every branch.
You can also run ./ct3-update.command trunk to update just the trunk, or ./ct3-update.commandmyBranch to update just the branch called myBranch.