In reply to Zi Yang.

Distributing 'premium' GPL licensed themes is not stealing at all.

It is also not unethical. The license the author distributed it under, of their choosing, explicitly allows this, gives permission for it.

Just because someone didn't truly understand the license when they applied it to their product, doesn't mean other users, whose actions are permitted by the license, are acting 'unethically'.

You should take a little more time, and consider the nature of open source, if you believe this to be unethical.