SCO's Linux licensing efforts look set to go up in smoke, as a revelatory email that claims 'no evidence of any copyright infringement' was found in a 1999 comparison of UNIX and Linux code.

SCO's suit against IBM now includes $3bn of copyright damage, but this is put down to IBM's continuing its AIX business, subsequent to SCO pulling IBM's Unix licence.

What the email does appear to destroy is SCO's campaign against Linux, claiming that the operating system contains Unix copyright code, and its efforts to extract licence fees from Linux users in respect of continued use of this code.

The email in question was forwarded to SCO CEO Darl McBride by Reg Broughton on 13 August 2002, sent to him the same day by Michael Davidson. It related to an investigation carried out in 1999 to compare contemporary versions of Red Hat Linux and Unix for evidence of copyright infringement.

Davidson says in that email that the investigation was entirely fruitless. 'At the end we found absolutely *nothing*, ie no evidence of any copyright infringement whatsoever'.

SCO has since rebuffed this, claiming that 'Mr. Davidson's e-mail is referring to an investigation limited to literal copying, which is not the standard for copyright violations, and which can be avoided by deliberate obfuscation.'

Yet Davidson describes the aim of the investigation as just that - to look for evidence of copyright infringement: 'a result of SCO's executive management refusing to believe that it was possible for Linux and much of the GNU software to have come into existence without *someone* *somewhere* having copied pieces of proprietary UNIX source code to which SCO owned the copyright.'

SCO in turn produces a draft report of that investigation, which indeed adds a number of caveats as to the potential of evidence of copying found. But why would one direct an investigation to concentrate on redundant evidence of 'literal' copying, when the actual purpose is to find evidence of copyright infringement?

Yet that draft report does indeed find evidence of copying. 'Many portions of the code were written with access to a copy of Unix sources... there is some code which is line for line identical to Linux ... there are also portions of the programs which appear to have been rewritten, perhaps only for the purpose of obfuscating that the code is essentially the same,' it reads. 'There can be no doubt that parts of the Linux distribution were derived from Unix.'

But it adds a number of caveats. 'It is possible that some of the code came from Berkeley or other third party... It is also possible that the code is exempted by the BSDI/Berkeley settlement.'

But what should be noted is that this is a draft report of the investigation sent from Robert Swartz to Steve Sabbath, SCO's General Counsel, 4 October 1999. The Davidson claims that the report found no evidence of copying were sent in 2002, so such comments presumably refer to a final version.

Yet Davidson says he doesn't have a copy of this final report, and is not even sure that one was ever produced.