it is possible to change wordpress theme and sell second time without any problem of copyright

You are just trying to game the system.

Asking the seller would be right - you would get a clear cut answer.

What you could do is learn from the source code and build your own from scratch.

Cheers!

- faceplam-

It was kinda funny that you even asked this question. To tell you the truth, a LOT of people actually do this. I have been creating websites since 2008 and I have seen clients asking me to change the existing template and then installing it on their next client's WordPress website.

However, in principles or ethics or whatever you call it, its WRONG. When you buy a theme from somewhere, you can use that theme on ONLY a single domain and not on multiple domains. However, its not possible to check that since no one can track who made that site, where did that template came from or whether that person has a pet dog or a cat.

Just take a scenario where you have Client A and Client B, you give them the same theme, same styling, same colors, now suppose client A and B meet and share their websites (coincidences happen), they would be like WT*.

They would just come to a conclusion that you scammed them (which is actually right). They won't use your service ever and instead warn people against you. Now don't take this lightly. Just like every drop of water makes an ocean, every negative impact on a client creates a problem for you which you might not care for at that moment since you might think "oh its ok I will move on to the next one".

The best way to go forward it to create themes yourself, learn some coding, starting from HTML and CSS, and then PHP or advanced scripting languages. Try cloning sites as a practice. Hard work pays ! You work hard you will go ahead a lot, you try to take the shortcut you will be sent back to the starting point.

just ask whomever you bought that from to please give you a refund or switch it out for another one. You cannot sell it unless you bought it with resell rights.