Haibun is a prose poem that uses embedded haiku to enhance the composition's overall resonance and effect. And that's all that we will leave you with. English language haibun is an evolving and highly complex form of writing and if we start delving into the various definitions, do's and don'ts, is and isn't, we may never be able to enjoy what the form may stand for.
The haibun contained in the first ten issues would give you a fair idea of what we are looking for. Surprise us, move us, shock us, just do not maintain the status quo. As for the haiku in the haibun, we believe it to be an integral part of the composition. It should move the story forward or take the narrative in a different direction. It may add insight or another dimension to the prose, resolve the conflict in an unpredictable way, or may question the resolution of the prose.
It's perfectly fine with us if the haiku does not work as a standalone piece of poetry, if it makes sense in the overall narrative and follows the other aesthetics of a haiku, we are open to it. But, yes 5-7-5 is usually not a haiku.