Annoying messages, try in a terminal, check permissions and dot-slash to run
looks like this here : http://imgur.com/DzS5Jmt
Not something I use, this one just compiled in an old laptop with Gimp 2.9.5 (otto ppa) installed.
Remember to unzip, check permissions. It starts but not really tested.
For some reason if installed in the gimp profile ~/.config/GIMP-AppImage/2.9/plug-ins/ it does not register
so make a plugin folder and add in the preferences settings.
Some plugins work, some do not, so the usual guarantee, there is none