Hi,
Firstly apologies for the confusion, this is still work in progress and we are hoping to get a preview release of this stuff out in the next few weeks.
The PHP SDK is made up of two parts. One is the PHP library, our PHP API implemented in PHP using web services to communicate with the repository. This can be used in your regular PHP environment.
The second part is the PHP AMP. This is an extension package for the repository that embeds the Quercus PHP implementation and allows PHP to be executed natively against the repository (hence all the Java!). The same PHP Alfresco API is available when running these native scripts so the aim is that Alfresco PHP scripts can be executed against either the remote PHP library or locally within the repository against the equivalent native implementation.
The side effect of having a PHP implementation in the repository is that Alfresco templates and scripts can also be implemented in PHP as well as the currently supported JavaScript and Freemarker.
Hopefully when the first release emerges this will all become clearer.
Cheers,
Roy