In reply to Zi Yang.

The best example of this is sites that redistribute GPL themes for free.

WordPress.org distributes GPL themes for free. Are they being unethical? There is nothing unethical about distributing GPL licensed software for free. This is specifically allowed under the licence. Anyone who finds this unethical or frowns on it doesn't understand the licence.

There are software licenses that prohibit the redistribution of software. The GPL is not one of them.