I think it should be possible. Including the JNP library in the application's library (for example .war/WEB-INF/lib/ or .ear/lib/) should make that library available for use. You could then use the code in AS 7 to do a JNP backed lookup (using the right initial context factory property value and the provider url) to make it as if the call is happening from some standalone client to AS4.x. But it's just a guess and it's likely that it probably will run into some issues that I haven't thought about.