So, Ninjakit is just a plugin..? Anyway, NinjaKit.safariextz is what I got and placed it at Safari extensions. So is Viewtube supposed to install by itself when I click the icon..? At least having done the previously mentioned things Youtube didn't start working yet... (I also thought I'd need Tampermonkey and that seems to be in place)Once you've installed NinjaKit go to http://isebaro.com/viewtube/
click on the Viewtube icon at the top, a window will open then install the script - that's it.