Apple has the right to continue restricting its operating systems to its own hardware thanks to a decision handed down by the Ninth Circuit Court of Appeals on Wednesday. Circuit Judge Mary Schroeder wrote in her opinion that Apple's Mac OS X licensing agreement was indeed enforceable against Psystar, which had sold non-Mac computers with Mac OS X installed.

Psystar had previously been held in violation of Apple's copyrights by a District Court, and did not appeal that ruling. Instead, in its appeal, Psystar argued that the OS X licensing agreement was an "unlawful attempt to extend copyright protection to products that are not copyrightable"—an argument that the Ninth Circuit has now dismissed.

The legal row between Apple and Psystar began in July of 2008, several months after Psystar introduced a bargain-basement computer for $399 that could run Mac OS X 10.5 (Leopard). Apple sued, and Psystar's original countersuit against Apple was thrown out completely; a bankruptcy filing later revealed that Psystar owed its law firm more than $88,000. All the while, Psystar continued to sell its products and even marketed new ones, such as an Xserve clone and an EFI tool meant to help individual users put Mac OS X on their hacktintoshes.

In late 2009, US DIstrict Judge William Alsup ruled that Psystar violated Apple's copyrights when distributing Mac OS X with its machines. Psystar's counterclaims were dismissed and the documents were sealed at Apple's request—the company argued that the filings might reveal some of the proprietary technical measures it used to limit the distribution of Mac OS X on unauthorized machines.

Psystar never appealed the decision that it had violated Apple's copyrights, but it did argue that Apple was engaging in anti-competitive copyright misuse by limiting its software to Apple hardware. The company claimed it had purchased copies of Mac OS X and included them when it sold non-Mac computers to customers, which should be protected under the First Sale doctrine. Judge Schroeder sided with Apple, however, which said Psystar hadn't shown evidence that the OS X licensing agreement restricted creativity or competition.

"Apple's [software license agreement] does not restrict competitor's ability to develop their own software, nor does it preclude customers from using non-Apple components with Apple computers. Instead, Apple's [software license agreement] merely restricts the use of Apple's own software to its own hardware," Schroeder wrote. "Psystar produces its own computer hardware and it is free to develop its own computer software."

Chicago-based intellectual property lawyer Evan Brown described this decision as "kind of a big deal."

"This is an important win for Apple because it bolts down the legal substrate for Apple's tightly controlled, closed ecosystem. Since the courts have found that Apple is not playing unfairly by keeping its users from loading Apple software onto non-Apple hardware, the company can likewise maintain the technological controls to ensure that only approved applications are used in connection with the operating systems," Brown told Ars. "A world in which there were legitimate marketplaces for third-party hardware running Apple software would greatly lower the entry barrier for hackers and enthusiasts to play outside of the rules. This court decision keeps those rules firmly in place."

The only part of the District Court's decision that Schroeder didn't agree with was one that sealed the judgement documents. She wrote that the court failed to articulate specific reasons for complying with Apple's request, and therefore vacated that part of the ruling and remanded it for further consideration.

As we noted in 2009, when Apple won its first round against Psystar, the decision will certainly limit companies that try to make a commercial business out of re-selling Apple's software with unauthorized hardware. What it won't limit will be hobbyists creating their own hackintoshes at home using their own PCs and OS X installations. In fact, the commercial industry has largely moved on already by selling tools to those at-home hackers (instead of the software and computers themselves), making enforcement of Apple's licensing agreement effectively moot for those users.