A US appeals court rejected Apple Inc.'s attempt to persuade it that security startup Corellium Inc. violated its copyrights by emulating its iOS operating system to assist researchers in discovering security weaknesses in Apple devices.

According to the US copyright fair use concept, Corellium's recreation of Apple's system was legal according to the 11th US Circuit Court of Appeals, advancing scientific research by supporting critical security research.

Florida-based With the help of Corellium's software, users may run iOS on non-Apple devices and analyze and alter the operating system in ways that make it easier for security researchers to look for flaws. In 2019, Apple filed a federal lawsuit against Corellium in South Florida for copyright infringement.

Prior to initiating the complaint, Apple made an unsuccessful attempt to purchase Corellium for close to $23 million, according to the appeals court.

In 2020, the district court rejected Apple's arguments regarding Corellium's iOS simulator. In 2021, Apple appealed.

The 11th Circuit determined on Monday that Corellium used iOS fairly and added additional features to its software that enable security researchers to "do their work in a way that physical iPhones just can't."

Apple claimed that Corellium merely repackaged iOS in a different format for financial gain, damaging the market for its operating system and its security-research initiatives. This claim was dismissed by the appeals court.

Corellium "opened the door for deeper security research into operating systems like iOS," the circuit court said.

The appeals court remanded the case to the district court so that it can determine whether Corellium violated the copyrights for Apple's wallpaper and icons or whether it assisted in infringement by third parties.