Can OSI specify that public domain is open source?

[Thorsten Glaser]

John Cowan <cowan <at> mercury.ccil.org> writes:

> Thorsten Glaser scripsit:

> > If some (non-government) US American were to take VistA, change some
> > amount of work in it, then publish the result -- with his changes
> > under say the BSD licence -- what's it then, to us non-Americans?
> 
> A work belonging to that American, but licensed to you under the terms
> of the BSD license, assuming the BSD license is valid in Germany.  The
> same would be true in the U.S.

So his actions would magically enable us to use the larger work?
What amount of work are we talking here?