Joomla and GPL license
 

Juts to make it clear before you start asking the same questions like on Joomla Forums

Joomla is free and is under GPL license (you are free to distribute it)
GPL doesn't mean you are not free to charge for your joomla extensions
Joomla templates are in a unique position because a partial code from index.php is GPL.
Example:
But images, css, javascript etc are not restricted to GPL licensing.

What does it mean? It means that you can freely distribute parial code from index.php but not the commercial images , css or javascript provided by us, unless we state that it is GPL