We don't need author's permission for use of they're characters.
It might seem rude to use them but it's all in the best interest of the story.
If it's necessary too kill them, then so be it.
Just don't make them die at random and it will be ok.
They abandoned the story so I imagine they could care less about they're character.

And I've very much enjoyed reading the past two posts.
Thank you for keeping this story alive.