by Stéphane Faure.
Hi Greg,
If you want just to create data in Moodle like create users, courses... (more details here : http://www.myddleware.com/solution/connected-applications?view=project&id=14:moodle), you can only use Myddleware. No need to install the plugin.
But if you want also to read the user's completion or their last access to a course because you want to send these informationin another application, in this case, you have to install the plugin in your Moodle to install these 2 custom webservice.
I hope it is clear otherwise don't hesitate to come back to me.
Stéphane