Auto-install on import, if NavServices is available. Unless a "no navservices" flag is set Python automagically imports this module so code that uses macfs.xxxGetFile will get NavServices dialogs.
diff --git a/Mac/Lib/macfsn.py b/Mac/Lib/macfsn.py
index f7b6b2e..3c12646 100644
--- a/Mac/Lib/macfsn.py
+++ b/Mac/Lib/macfsn.py
@@ -129,6 +129,7 @@
 	StandardPutFile = _StandardPutFile
 	SetFolder = _SetFolder
 	GetDirectory = _GetDirectory
+	_install()
 else:
 	from macfs import StandardGetFile, PromptGetFile, StandardPutFile, SetFolder, GetDirectory