Apple's forthcoming release of Mac OS X 10.5 Leopard is the first BSD-based operating system to receive the UNIX 03 certification, placing the Mac maker among an elite group of official UNIX 03 vendors.
"All that is changing," explains Ars, "since the upcoming Leopard release has received the UNIX 03 certification as of May 18, meaning that Mac OS X 10.5 on the Intel platform is a 'true' UNIX OS, rather than just being UNIX-like."
From a developer standpoint, UNIX 03 certification means that Leopard conforms to the Single UNIX Specification Version 3 (SUS), which outlines how components like the shell, compiler, and C APIs should function.
In becoming the first BSD-based OS to receive the UNIX 03 certification, Leopard also adds Apple to an extremely short list of official UNIX 03 OS vendors that include IBM, Sun, and HP. This presents several advantages:
"Any software written for the SUS specification is easily portable to a UNIX 03 operating system, meaning that enterprise customers who need a 'real' UNIX for their applications can now use Leopard servers if they so desire," writes Ars. "Leopard's certification also gives developers another option for a development platforms, which could translate into some extra Mac sales."
Leopard's UNIX 03 certification applies only to the Intel-based version according to the official Open Brand Certificate [PDF].