What’s the terms of use for themes? Is it GPL?

Hi,

I would like to know the terms of use governing the iDream theme or any other themes. As WordPress is under GPL, does the themes automatically fall under GPL?

I’m interested to use iDream theme for corporate blog (open to public), hence would like to know what licensing it’s under. Tried to contact the designer of the theme but can’t find any contact information.

Hope someone clarifies, thank you.