Based on quotes from SCO officials (both in print and at conferences), the author postulates that one of the reasons that SCO has refused to present information publicly is that not even the company knows where some of the code comes from. So far, indications are that SCO may well have just looked for similar bits of code and claimed infringement when they found it. This leaves open the possibility that the code was misappropriated in the other direction (i.e. SCO is in violation of the license agreements of other parties in including it in their "UNIX" codebase).
Whatever the case, the folks at SCO aren't doing anything to make the situation easier (such as providing documentary evidence in a public forum) and it appears that they are hell-bent on continuing the confusing state of affairs in hopes that it may extort more money from the public and delay the patching of Linux to remove any code that actually infringes (thus making the system clean).