Later this year we will see the much anticipated release of Magento version 2. This promises some exciting changes which should make Magento leaner and more developer friendly.
Of course having to wait until the end of the year to get our hands on Magento2 to see what has changed and what as developers we will have to change in our own extensions isn't ideal so to help us with that Magento has started updating a development release which has been made available on github at https://github.com/magento .
You will see that their are two magento repositories there; 'magento2' and 'taf'. clone the magento2 repository and you can install as usual. DON'T put this into production! It is an early release and only some parts are implemented but you should be able to update as new commits are made.