SCO's contract dispute with IBM has been accompanied by a smear campaign against the whole GNU/Linux system. But SCO made an obvious mistake when it erroneously quoted me as saying that "Linux is a copy of Unix." Many readers immediately smelled a rat--not only because I did not say that, and not only because the person who said it was talking about published ideas (which are uncopyrightable) rather than code, but because they know I would never compare Linux with Unix.
Unix is a complete operating system, but Linux is just part of one. SCO is using the popular confusion between Linux and the GNU/Linux system to magnify the fear that it can spread. GNU/Linux is the GNU operating system running with Linux as the kernel. The kernel is the part of the system that allocates the machine's resources to the other programs you run. That part is Linux.
We developed GNU starting in 1984 as a campaign for freedom, whose aim was to eliminate non-free software from our lives. GNU is free software, meaning that users are free to run it, study it and change it (or pay programmers to do this for them), redistribute it (gratis or for a fee), and publish modified versions. (See an overview of the GNU project.)
In 1991, GNU was mostly finished, lacking only a kernel. In 1992, Linus Torvalds made his kernel, Linux, free software. Others combined GNU and Linux to produce the first complete free operating system, GNU/Linux. (See our GNU/Linux FAQ.) GNU/Linux is also free software, and SCO made use of this freedom by selling their version of it. Today, GNU runs with various kernels including Linux, the GNU Hurd (our kernel), and the NetBSD kernel. It is basically the same system whichever kernel you use.
Those who combined Linux with GNU didn't recognize that's what they were doing, and they spoke of the combination as "Linux". The confusion spread; many users and journalists call the whole system "Linux". Since they also properly call the kernel "Linux", the result is even more confusion: when a statement says "Linux", you can only guess what software it refers to. SCO's irresponsible statements are shot through with ambiguous references to "Linux". It is impossible to attribute any coherent meaning to them overall, but they appear to accuse the entire GNU/Linux system of being copied from Unix.
The name GNU stands for "GNU's Not Unix". The whole point of developing the GNU system is that it is not Unix. Unix is and always was non-free software, meaning that it denies its users the freedom to cooperate and to control their computers. To use computers in freedom as a community, we needed a free software operating system. We did not have the money to buy and liberate an existing system, but we did have the skill to write a new one. Writing GNU was a monumental job. We did it for our freedom, and your freedom.
To copy Unix source code would not be ethically wrong, but it is illegal; our work would fail to give users lawful freedom to cooperate if it were not done lawfully. To make sure we would not copy Unix source code or write anything similar, we told GNU contributors not even to look at Unix source code while developing code for GNU. We also suggested design approaches that differ from typical Unix design approaches, to ensure our code would not resemble Unix code. We did our best to avoid ever copying Unix code, despite our basic premise that to prohibit copying of software is morally wrong.
Another SCO tool of obfuscation is the term "intellectual property". This fashionable but foolish term carries an evident bias: that the right way to treat works, ideas, and names is as a kind of property. Less evident is the harm it does by inciting simplistic thinking: it lumps together diverse laws--copyright law, patent law, trademark law and others--which really have little in common. This leads people to suppose those laws are one single issue, the "intellectual property issue", and think about "it"--which means, to think at such a broad abstract level that the specific social issues raised by these various laws are not even visible. Any "opinion about intellectual property" is thus bound to be foolish. (See our list of words to avoid.)
In the hands of a propagandist for increased copyright or patent powers, the term is a way to prevent clear thinking. In the hands of someone making threats, the term is a tool for obfuscation: "We claim we can sue you over something, but we won't say what it is."
In an actual lawsuit, such ambiguity would make their case fail, or even prevent it from getting off the ground. If, however, SCO's aim is to shake the tree and see if any money falls down, or simply to spread fear, they may regard vagueness and mystery as advantageous.
I cannot prognosticate about the SCO vs IBM lawsuit itself: I don't know what was in their contract, I don't know what IBM did, and I am not a lawyer. The Free Software Foundation's lawyer, Professor Moglen, believes that SCO gave permission for the community's use of the code that they distributed under the GNU GPL and other free software licenses in their version of GNU/Linux.
However, I can address the broader issue of such situations. In a community of over half a million developers, we can hardly expect that there will never be plagiarism. But it is no disaster; we discard that material and move on. If there is material in Linux that was contributed without legal authorization, the Linux developers will learn what it is and replace it. SCO cannot use its copyrights, or its contracts with specific parties, to suppress the lawful contributions of thousands of others. Linux itself is no longer essential: the GNU system became popular in conjunction with Linux, but today it also runs with two BSD kernels and the GNU kernel. Our community cannot be defeated by this.