I find SCO vs. IBM far more telling of the easily-exploited nature of the USA's (a) court system and (b) bankruptcy protection laws, than of anything related to what is a good contribution policy. IBM clearly thought it had a sound position when contributing the code in question to the Linux kernel; SCO acted as if it thought differently, and was able to spew sufficiently convincing legal bafflegab to persuade a (possibly overly-sympathetic) judge that their case was not completely devoid of merit. It's not clear what Linus having a copyright assignment requirement would have done to avert SCO v. IBM, unless it prevented IBM from ever participating in the first place.
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