Download Android Source

First install git 1.7, java 1.6, and python 2.7.

mkdir ~/bin
PATH=~/bin:$PATH
curl https://dl-ssl.google.com/dl/googlesource/git-repo/repo > ~/bin/repo
chmod a+x ~/bin/repo
mkdir androidsource
cd androidsource
repo init -u https://android.googlesource.com/platform/manifest
repo sync

For more details visit: Initializing a Build Environment