the U.S. military most likely having an interest in suppressing information to avoid someone else creating AI first.

someone else creating ai first? You make it sound like they are trying to create general ai skynet...

  there are strong incentives for secrecy (trade secrets)

they do not have the right to call themselves "open" if they are focusing on secrecy. They are trying to paint themselves in a positive opensource light when really they are no different then any other corporate overlord hiding in the shadows. Open implies developed in the open, free for use + modification, and/or key details NOT being hidden from the public. Simply sharing details of things created or research done is no different than what researchers at any other ABC corporation/organization do.