Hi Scott,
to create an 'uploads' folder in /server/webapps/ROOT/, the server plugin is relying on a path relative to the executable.
On WIndows/Linux launched from developer, this path resolves correctly, but on Mac OS X, it doesn't since the executable is located in the Servoy.app bundle: Servoy.app/Contents/MacOS so the plugin was falling back to the home of the current user (have a look inside yours, you should have and uploads folder in there with your transferred files).
I have corrected this so that it take the Mac path into account, try the attached jar.
Johan: a patch follows