cmb package on mac does not include smtk plugins
I pulled the mac installer from the website (July 30 2015), and the package does not have any smtk plugins anymore, which means ModelBuilder can't load anything. I also had a dmg from April, which has plugins under ModelBuilder.app/Contents/Plugins. This needs to be fixed asap.
The windows installer does have those plugins installed, so this seems to be an issue with packaging on mac.