> And this is the part of the criciticm of copyright assignment that I
> don't get. If we really believe in our FOSS licenses - and we should,
> otherwise why use them - then they will preseve our freedoms in both
> copyright assignment projects or in non-copyright assignment projects.
Ah - you are one of the 'too nice' people that hasn't twisted their brain around the tortured world of proprietary contracts. As soon as a company steps away from a transparent, open Free Software license - the proprietary license will almost certainly have "non-fork" provisions - such that these guys are bound to the other side of whatever fork you do. So - sure, of course you always have the right to fork: but the effectiveness of doing that on your own is going to be small, and you may find you have a set of stake-holders that agree with your direction; but simply cannot help you due to their proprietary license agreement.
So - the 'additional' licenses, people get, often do not simply give people the ability to re-use the code in proprietary software; but bind them in many other, un-acceptable ways.