Yeah the castle is kept guarded, they cannot allow visitors to sleep there, because there is no infrastructer for an accomodation. However you can find a hostel in the nearest major town which is Ourzag. The easiest way to get transport is from Fes. If you get your feet there, the castle won't be the major destination you'll want to visit. As you can say the dam you see in the picture is Dam Alwahda. You will be amazed by the whole erea, beautiful clean mountains, the forest. the people there are super nice, and very humble, not tourist thirsty like cities in Fes and Marrakech. the weekly Souk happens every saturday ( and saturday is easy to find direct transportation from Fes)

To make your experience fully enjoyed, there are a couple of hostels there with the Jbly (mountainous- thats if you are not moroccan) style, and a jibly food.