No, obfuscation's not gonna help.

How they build and sales a product with no code "protection" ?

With licenses, I guess.

To give you a specific case (and one that may not adapt to your philosophy), in the company I work at, the client always gets the code and the right to change it (the caveat being that as soon as he modifies it we are no longer liable for the malfunctioning of the system). The one thing he cannot do, because it is stated in the contract, is to sell the code to someone else (this, of course, simply put, because the contract has more words).