PureMVC has grown from being a simple solution for Flex/Flash and AIR developers to write more maintainable AS3 client code to being a solution for client or server applications on many platforms.
With many open-source offerings, the API docs, code, and some samples are all you get. With PureMVC, the goal was to go a step further and provide guidance in the use of the framework and a better 'big picture'.
The documentation you see on the menu here currently relates to the AS3 implementation in specifically in its examples, but the framework is quite general. And though each port (such as Java or PHP) will certainly have slight unavoidable differences the actors and their roles, responsibilities, and collaborations are the same in every implementation.
So, for now, Pythoners, PHPers and GWTers, don't be afraid to dive into these documents. Though you might not know ActionScript, it won't get in the way of your getting the really important concepts. As the communities grow around each port, we will hopefully get these documents ported as well.
The Implementation Idioms and Best Practices (IIBP) document has been translated into a number of languages available from the menu. Currently, they all feature examples in AS3, except for one: the JS / Adobe Forms version. Please note that this document is very specific to the Adobe Forms environment, and as such is not otherwise very useful, even to PureMVC / JS programmers, since the DOM and event model is not the same as that in a browser.
Also note that the API documentation for each port or utility is available on the project's page in the 'Code' section of the site.