So many developers have huge egos. All they care is $? What about the community that gave you the ability to create those themes and make money?

I think all themes/plugins from any CMS inherit the same license their "master" CMS.

Drupal themes/plugins inherit Drupal Licenses
Joomla thenes/pplugins inherit Joomla Licenses

and so forth.

If you meet a developer with a super inflated ego, guess what? move on to the next one.

You can create the best theme/plugin/etc...in the whole entire universe but if your ego gets in the way, no one will buy it.

No one buys it means your theme/plugin/etc... will be as useful as a thong on an Antartican penguin.