Food Lion, a supermarket chain, has been using the familiar ANDY GRIFFITH SHOW theme music in its radio and television advertising lately. Did they pay
for the use of it or is it now in the public domain? A few years ago, it was
definitely NOT in the public domain because I have a DVD and a video tape
with different music on it (I assume, at that time, the episodes were public
domain but the theme song was not). So what's up with that? Anyone know?

As far as I know the theme music copyright is still in force.
You are right about the episodes and music. Sixteen eps from season three fell out of copyright protection due to an error and are now in public domain. Anyone may make and sell copies of them without paying royalties. The music is under separate copyright and rather than pay to use it, most producers of those sixteen eps opt for other music.
I imagine Food Lion is paying to use the music.

As far as I know the theme music copyright is still in force.
You are right about the episodes and music. Sixteen eps from season three fell out of copyright protection due to an error and are now in public domain. Anyone may make and sell copies of them without paying royalties. The music is under separate copyright and rather than pay to use it, most producers of those sixteen eps opt for other music.
I imagine Food Lion is paying to use the music.
Thanks for the info.