Are chatbots based on deceased loved ones healthy? I recently read an article about a journalist who created a chatbot to ensure that a conversational entity with elements of his dying father's personality would exist even after his father--terminally ill with cancer--passed away.

I am a software engineer experienced with creating chatbots and it has crossed my mind to create one for the parents of my best childhood friend who was killed 10 years ago in a car accident. 

I speak to the parents a few times a year and we have a great relationship. Having been their son's best friend when we were growing up, I know his mannerisms and expressions almost as well as they do so I am confident that I could do a good job of training the chatbot.

That said, the parents have found their peace with my friend's passing and I don't want to do anything to jeopardize that. In any case, I would obviously discuss with them before creating such a chatbot. This leads to my ultimate question:

Would creating a chatbot based on a deceased loved one help or harm those of us left behind?

I really don't know the right answer to this. In my most generous thoughts of how this turns out, it could give his parents, siblings, and future family members a way to remember/meet his fun, goofy personality, but I could also see this opening old wounds.
In my opinion, it depends on whether they would like the AI to synthesize novel thoughts/opinions or to merely contextually quote a history of that individual's textual recordings.

Making a value judgement here, I would say than an AI saying "I forgive you." (from beyond the grave) is not healthy.

But if the chatbot acted as a way of indexing into the individual's actual history, then all potential errors become ones of context (and not content).
(This level of reproduction may not be totally necessary depending on the users' sensitivity to cognitive dissonance, but I would personally feel slimy if I tried to pass off a markov chain of scripts and data as my friend.)

If you're open to alternatives to chatbots, I would suggest that you frame the project as a tribute to your friend's life; even a simple collection of stories from your time together could have a powerful (healthy) impact on the grieving parents.