UNIX 03 is the mark for systems conforming to version 3 of the Single UNIX Specification.  Hence, a vendor's operating system that attains the certification will:

• Comply with the specification
• Continue to comply with the specification
• Fix any issue in a prescribed time period if in a non-compliant state

A few quotes from Yager's post
"OS X's commercial credentials recently got a major boost from the Open Group. Thanks to the efforts of Apple's OS boss Kevin Van Vechten and his team, Leopard has cleared all of the hurdles required to attain UNIX 03 certification. That places Apple in elite company. Only Sun, IBM and HP are certified, so OS X turns the Big Three into the Big Four."

"There are UNIX pretenders, and there is the real thing. Mac users, realize that qualifying for UNIX is no small feat, especially for an open source, BSD-based OS. The Open Group standards, the PDFs for which are idiotically marked as free but blocked from PDF download unless you buy your way into a membership, are rooted in System V. Apple is to be commended."

The UNIX 03 specifications cover libraries, system calls, terminal interfaces, commands and utilities, internationalization and the C language. That's the whole enchilada for ISVs (independent software vendors) porting their server and non-GUI applications to OS X. UNIX ISVs ought to climb on board, because once Leopard ships in October I expect Xserve sales to take a leap. Software developers should also keep in mind that the Leopard client OS is the same as Apple's server, minus the quite exceptional administrative tools, and the installed base of four and eight-core Mac Pro desktop/workstations is even larger.

You can read the article in full at the Enterprise Mac Blog.  Click the following link to learn about  UNIX 03.

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This is a great achievement for Apple and Mac OS X.  Now with UNIX 03 certification, Mac OS X will be given additional consideration at the enterprise level.  In numerous articles on this site we have expressed our views that Mac enabled enterprise was not only beginning to take shape but also will also gain momentum moving forward.  Be sure to check out our comments under the articles posted to the Enterprise category.  Articles of note include:

• Computerworld: Mac OS X an ideal platform for Small Business
• Auto Warehousing Co. drops Windows PCs for Apple Macs
• Macs are Faster - Benchmarking - Virtualization Technology - Increased Market Share