Linux revision control
Little-known (but not AFIAK secret) fact is that Larry McVoy (Bitkeeper) has been tracking changes to the kernel source for years. Sort of a pre-adoption proof-of-concept of BitKeeper, not to mention the sort of thing which might become commercially valuable to a party that wanted to track its own deltas to the core tree (this is one of the features of BitKeeper -- making and tracking satellite repositories with one-way transitivity to core is reasonably trivial)...or a large monied interest with an interest in legal discovery.
\r\n\r\nAnother interesting point this raises is the question of who is responsible for introduction of encumbered code into the kernel. SCO is certainly making the case that it's IBM. However one possible legal argument is that the code submitter him- or herself is representing the code to be legally clear, and assumes responsibility in the event that it is not. Time will tell.
