It's because Maverick does not have the Java tools anymore (like Maven, Ant, ...) pre-installed. What works for me whas:
brew update brew install ant
Then, you might need to do the following to add the "ant" to the default path (that SuperAnt seems to be using)
sudo ln -s /usr/local/bin/ant /usr/bin/ant
Here are some links talking about the various ways to install Ant on Mac.