> However, this is still necessary in case we share some generated sentences in social media or so (like we're doing on twitter now).
This is something that you should only do with the permission of the user who provided the voice. You don't need generalized permission to do that for every user, and given the nature of the technology, you shouldn't ask for such permission.
> This is what our lawyers suggested to protect ourselves.
Generally speaking, a lawyer's advice is going to be optimized for maximum protection in possibly unforeseeable circumstances, not for what might actually be needed or even reasonable to request of every user.
Generally speaking, companies aren't going to go out of their way to rein in their lawyer. Most people won't even read that fine print, unfortunately.
This is something that you should only do with the permission of the user who provided the voice. You don't need generalized permission to do that for every user, and given the nature of the technology, you shouldn't ask for such permission.