@joedolson - we hook into bits like save_post, but then we never fire publish_... actions so not sure how your plugin is getting triggered.
@owcv - I'd need to test this out myself to make sure, but this won't be something I can get to immediately. Am keen to make sure EM works with good/popular plugins so will certainly get to it asap.
r.e. duplicating, I think making it a draft by default makes more sense than publishing it immediately so will look into this in an upcoming update.
in the meantime, you could always set the post status to 'draft' and also $EM_Event->event_status to 0 by hooking into this:
$EM_Event is essentially an extended post object.