there is a wiki page ( install only from svn)http://en.wikibooks.org/wiki/Celestia/D ... S_platform
but the wiki needs a mac section
Linux and Windows both use the celestia/extras/ folder
Mac's do not
it would not be possible to have both in the same zip file
All of my add on's extract to /extras/JohnVV/ ( except for some old ones that have not been updated)
and most extract to /extras/"It'sName "