Abdul Qadeer Khan talked to reporters immediately after a court ordered his confinement ended, ABC News reported.
"Are they happy with our God? Are they happy with our prophet? Are they happy with our leaders? Never," Khan, 72, said."So why should we bother what they say about us?"
When it comes to the opinions of former U.S. President George W. Bush and former Vice President Dick Cheney, Khan snapped '" damn don't care."
Khan, known as the father of Pakistan's nuclear weapons program, had been held in detention for five years for his alleged role in sharing nuclear technology with Iran, Libya and North Korea.
Khan was freed on an order from Sardar Muhammad Aslam, chief justice of the Islamabad High Court, the Financial Times said.
Khan refused to respond to questions about the allegations against him. U.S. officials say that he remains a danger with a high risk of selling nuclear information.
Khan joined the Pakistan nuclear program from the Netherlands, where he was working as a metallurgist, when it was created in response to a nuclear test by India in 1974. Pakistan made its first nuclear tests in 1998.