@Constance Jeske Hi Constance, I believe because you are feeding him - he is slowly building up his trust towards you. And thus now, he is allowing you to touch his head for a moment. Feral cats avoid human contact but can become more comfortable around humans who feed them - but, will prefer to remain detached in the long term.
Also, just a thought: a scared stray cat can be misjudged as a feral, as the fear and/or defensive aggression he might display could be indistinguishable from the fear and/or defensive aggression displayed by a feral cat. However, given some time, most frightened stray cats will stop displaying violent fear to humans - while feral cats are most likely to only have extremely fearful and defensive responses to humans. Much like any wild Bobcat or Lynx would.