SCO–SGI code dispute of 2003

During SCO Forum, held on August 17 – 19, 2003 at the MGM Grand Las Vegas, SCO publicly showed several alleged examples of illegal copying of copyright code in Linux. Until that time, these examples had only been available to people who signed an NDA, which had prohibited them from revealing the information shown to them. SCO claimed the infringements are divided into four separate categories: literal copying, obfuscation, derivative works, and non-literal transfers.

The example used by SCO to demonstrate literal copying is also known as the atemalloc example. While the name of the original contributor was not revealed by SCO, quick analysis of the code in question pointed to SGI. At this time it was also revealed that the code had already been removed from the Linux kernel, because it duplicated already existing functions.

Within hours, the open source community started several different analyses of the infringing code. While the results of these analyses differ slightly, they all confirm that the code in question was derived from Unix code. These analyses also pointed out that while the code could possibly have originated in Unix, this does not necessarily prove infringement of copyrights.

The community was determined that this was a particularly bad example, because the code in question had never been used in the mainstream distributions of Linux, and had been present only in the IA-64 version. The relative sparseness of worldwide IA-64 installations, combined with the limited time in which the code was present in Linux, makes the chance of actually encountering a system running this code very slim.

While it is possible that the code contributed to Linux originated from UNIX System V, its original implementation happened in the early 1970s. Comparison of the original Unix source code and the UNIX System V source did not reveal any substantial differences between the two. In fact Dennis Ritchie, one of the creators of the original versions of Unix, acknowledged that either he or Ken Thompson wrote the original code from which the UNIX System V code is derived:

So: either Ken or I wrote it originally. I know that the comments that first appeared by the 6th edition were definitely written by me, since I spent some time annotating the almost comment-free earlier editions.

This is very important, because the original versions of Unix did not have any copyright claim in the source code. At that time the law required these copyright claims[1] which effectively means the early Unix code is not protected by copyright law. Additionally, both Santa Cruz Operation and The SCO Group released the source code to early versions of Unix[2] under a 4-clause BSD-like license, allowing the use of the source code in other open source products.

October 1, 2003, SGI responded to SCO’s allegations in an open letter to the Linux community. In this letter, Rich Altmaier, vice president of software, claims that these small code fragments were indeed inadvertently included in the Linux kernel:

All together, these three small code fragments comprised no more than 200 lines out of the more than one million lines of our overall contributions to Linux. Notably, it appears that most or all of the System V code fragments we found had previously been placed in the public domain, meaning it is very doubtful that the SCO Group has any proprietary claim to these code fragments in any case.[3]

• SCO-Linux controversies
• USL v. BSDi

• SCO's evidence of copying between Linux and UnixWare
• SCO's Evidence: This Smoking Gun Fizzles Out
• Analysis of SCO's Las Vegas Slide Show