Questions like this can only be answered by asking what the consequences of the categorization is. Does saying "religion" make it worth dismissing? Does it make it a rival to Christian thought? Does saying "philosophy" mean that it has no consequent prescriptions for living?

Categorization for its own sake is definitively useless. If you want to compare Heraclitus to Joshu, go for it. Alternately, if you want to compare Pirsig with Aquinas or Kant, fine. If you want to figure out how to live, there's not much point to asking, "Is it a religion?" or "Is it a philosophy?": the salient point is rather whether or not there's anything worth enacting in your life.