A thought about free software licenses
It's recently occurred to me that one way to think about the GPL versus BSD/MIT licensing issue is that they are embodying two competing bits of psychology: people want to share their work and have it widely used, and people don't like being taken advantage of.
(Although it may be surprising, there is quite a bit of evidence that we are in some sense wired to feel strongly about 'unfairness' and to punish it, even at a cost to our own interests. Psychologists have done a number of interesting experiments on this; see, for example, the discussion in here, or the discussion of the 'ultimatum game' in this Wikipedia article. Having your work 'taken advantage of' is a form of perceived unfairness.)
This implies that there is no global right answer for which software license to use, since people have different balances of these drives, so how they weight the various licenses will also differ.
(Then when people argue with each other over the license choice, each side can wind up in some sense arguing past each other, because the weights they put on low-level bits of psychology differ significantly.)