It'd be fine to not negotiate if you weren't going to use a voice that sounded famous. If I were offering something that let you make any kind of voice you want, I would definitely not market any voice that sounded familiar in any way. Let the users do that (which would happen almost immediately after launch). I would use a generic employee in the example, or the CEO, or I'd go get the most famous person I could afford that would play ball. I would then make sure the marketing materials showed the person I was cloning and demonstrated just how awesome my tool was at getting a voice match.

What I wouldn't do is use anything that remotely sounds famous. And I would definitely not use someone that said "no thanks" beforehand. And I would under no circumstances send emails or messages suggesting staff create a voice that sounds like someone famous. Then, and only then, would I feel safe in marketing a fake voice.

Not sure legally. I chose the words “perceived similarity” intentionally to encompass scenarios in which the similarity is coincidental but widely recognized. Even in that case, I believe the original person should be entitled to a say.