I think it's pretty clear Vinge is using FSF terminology ("free software" is free as in freedom, not as in free beer), so that software published without any copyright reserved would not qualify as free software. (It's not free because someone can capture it. He does that by extending it to the point of obsoleting the original, then restricting use of the extended code).
However, I think most of the wonderfulness he attributes to free software is really just the wonderfulness of software. And the few points that do involve copyright would hold just as well for public domain software as for free/copyleft/GPL software.
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