Sorry, but I have to say this bluntly: this is a stupid question/thread. Anyone with any knowledge of Sikhi can speak about it. Sikh or non-Sikh.
Sure, Amritdhari should run our gurdwaras, but it doesn't mean non-Amritdharis can't help out (let's be real honest here: most of the money and food contributing to gurdwaras are coming from non-Amritdharis). If Amritdharis have problems eating food from non-Amritdhari, then it's their lost. Langar is open for everyone to eat and serve food. There's no limitations besides making sure the food is cook properly.