I am sorry dozzie, did not want to be aggressive or dry, just I don't get what you mean. PJON works pretty much everywhere. The use you can do of PJON depends on your needs and the architecture that will execute it. In some cases PJON can be useful to "wire a bucket of Arduinos pin-to-pin to each other" but can also be used to create a virtual network computers running winx86, macosx or linux operating over the internet infrastructure. I think you would need some time to go through the available documentation and spec to have a clearer view of its features and limits.