Say you once wrote something with a friend that does not talk to you anymore, say you show it 10 years later to someone else. Say they want you to publish it.
Would you:
a) Publish on your own name without asking.
b) Publish on you own name without asking, but adding a thank you note.
c) Publish with both names without asking.
d) Ask
@faras D, but you probably want a lawyer to get involved.
@munin a lawyer ? for what? if he declines I can't use it, if the accepts then I need to share profit or what?

@faras To make sure that all parties involved are -extremely- clear on what the relevant responsibilities or potential profit-split terms would be.

An ounce of prevention is worth many pounds of cure in situations like this.