Bart
The KMZ that you export from MapRunF is just the Map. (Not the course) You can send it to your friend from them to set their own course using CheckSites.
In summary - If you want to share a course use CheckSites, and send your friend the 6-digit code. You can share the Map and the course in this way.
See:
http://maprunners.weebly.com/maprunf---event-options.html for a summary of the options and what is needed at each level.
Peter