Is changing the child theme function prefixes required before marketing a theme?

If I use a child theme as the basis for building a new theme is it required to change all the function prefixes to my theme name? I did not see this covered in the “Build Your Own Wicked Wordpress Themes” book. I know this would be a desirable thing to do but is it required and if just the name is changed, in the event the function is used as is, are there any legal implications?