> hmm, may be not all systems are as much populated (polluted? :-)
> by different packages doing similar things?..

Well, there is that.    But I look at it as

  there are a number of packages that meet some need.

  various other programs depend on various of these.

  a good packaging system should permit most of these to be installed,
  so that 'using programs' can be packaged without grief.

The lack of db 1.85 support is now causing coda grief, and it was this
that I was reacting to.   But now we are debating packaging philosophy.

> Hence we have to live in a non-perfect world of OSs and distributions.

True.  One might take Debian's dropping of 1.85 support as indication
that no reasonable program should be using it, too :-)

> Do not forget that any dependency on a certain OS or distribution, even on
> the hypothetical "right" one, reduces Coda chances to be useful and used.

Absolutely.  As a BSD user, I'm well aware of this since a distressing
number of people do not seem to realize there are OSes beyond Linux.
A real solution has to work on a wide variety of platforms.