So programs produced with taxpayer money should not be expensive,
because then only big companies will buy them, and they should not
be free of restrictions, because then "the big boys will run with
anything they find that's worthwhile."
  If big companies can't develop and sell "derived works", then
society at large will not even be given the opportunity to buy them.
They will only be useful to programmers for amusement.  I can't with
a straight face ask the public not only to subsidize my play, but to
not get any value from it.
  Maybe the NIH should not let drug companies develop vaccines based
on NIH research, but should only let competent researchers make the
vaccine in their own labs for their friends and acquaintances.

> > ignorant of the Netscape/U of Illinois story.
>
>Sorry, I'm afraid I don't know about that one.

  Some grad students working for the U of I wrote a graphic web
browser.  Jim Clark came by and said "let's start a little company
called Netscape and make a pile."  So they did, and the U of I was
not happy.  The taxpayers of Illinois paid for something, and the
profits went to Netscape.  If it had been GPLed, the WWW would have
remained an academic-only thing for a few more years, until
Microsoft caught on and built their own (or bought from somebody
who re-invented the graphic browser).

>"Legal copy" /= "nobody can be found to sue me".

  As a practical matter, what's the difference?  if you are really
just using one copy for yourself, do you think the
needle-in-a-haystack owner is going to find you, the
needle-in-a-haystack user?  Or going to waste time, when neither
of you has even tried to make any money, by filing suit for
non-existent damages?  But perhaps you intend not to just use it
yourself, but to distribute it around, and then you might be
found.  I suggest in that case you really *ought* to spend some
effort locating the owner.  Note that copyright violation is
not going to bring the cops - only the owner.

>In fact, I wrote to a receiver asking for a license for a copy
>of some software and got a letter back that said "We are unable
>at this time to sell you a license, and we will sue you if you
>obtain a copy illegally."
  Were they in the process of trying to get somebody to market it?
If nobody wants to market it, are they really going to sue you for
non-existent damages because you made a copy?  Lawyer stationery
comes preprinted with "We'll sue" - that doesn't necessarily mean
they really will. ;)