All of our downloads are hosted on Launchpad. Although these downloads do not necessarily reflect the latest changes to the library, you can still find downloads of the latest stable releases there.
Source Code Repository
To take advantage of the latest changes to Stack.PHP, you will need to check out a copy of Stack.PHP's Bazaar branch. If you have Bazaar installed, you can simply execute the following two commands:
bzr init bzr pull lp:stackphp
You can also browse the source code here.