I was about to buy a vhs/dvd combo machine to copy a porn tape or two
I bought years ago onto a dvd to send to a friend. This must be
technically impossible not to mention illegal. How about a brief
overview on the subject.

You have to buy a DVD burner.  What you describe is only a playback
unit.  Sony has a standalone DVD burner called the VRD-VC20 that goes
for about $230.  You plug it into your VCR and record on DVD+R or
DVD-R disks.  You can also plug it into your computer and use it as a
DVD drive.  Or you can buy a consumer DVD recorder that looks and
works like a DVD player.

As for legality, it's interesting to see that the recording industry
has scared everyone into thinking all copying is illegal.  The Sony
Betamax case allows you to make a copy for your own personal use.   A
lot of people are transfering their VHS and Beta tapes to DVD.  This
is perfectly legal.  Sony, which owns Columbia Studios, would not be
selling such a device if it wasn't legal.

What's not legal is to go around handing out copies or trying to sell
them at flea markets or on the street.  You can't mass produce them
and you can't sell them.

Most porno tapes don't have Macrovision, and most porno DVDs don't
have copy protection, so there shouldn't be any problems copying the
tape or ripping porno DVDs.  Most DVD burners won't be affected by
Macro either.  But you can buy a video stabilizer if you have a
problem with other tapes.