Which theme to use for a custom theme?

of course I do not wish to reinvent the wheel, when people make custom WP themes they surely start with another theme.

What is a good starting theme to revamp

 

Best theme to start with is the default theme. just edit what you want right onto that.

 

But if i wanted to license the theme myself under GPL this would be acceptable?

 

http://www.premiumnewstheme.com/canvas/

or

http://www.premiumnewstheme.com/thesis/