You can download the adobe_php_sdk.zip file immediately, extract it and explore the samples and demos immediately.
In true open source fashion, all the code in the project is currently available in various open source licenses, and the content for the HTML page is available under the Creative Commons license.
There is a project hosted at Google Code for the Adobe PHP SDK, and a mailing list at Google Groups as well."
You can download the (unofficial) Adobe PHP SDK from http://blogs.adobe.com/mikepotter/adobe_php_sdk.zip You can join the Google project at http://code.google.com/p/adobe-php-sdk/ and you can join the Adobe PHP SDK mailing list at http://groups.google.com/group/adobe_php_sdk/