I ran into a bit of a problem because I built graphics/gimp (GIMP 2.0.0)
(on NetBSD/i386-1.6ZK) and then wanted to install graphics/xsane and/or
graphics/sane-frontends.

Both xsane and sane-frontends depend on 'gimp1-base' which builds and
installs gimp v1.2.5, _overwriting_ the previously-installed gimp v2.0.0.

I pkg_deleted gimp-2.0.0 and noticed that it complained about not being
able to remove some gimp-1.2 directories(?).  I then re-built gimp
(v2.0.0).  xsane and xscanimage seem to still work and gimp 2.0.0 seems
to not be troubled by it.  Xsane/xscanimage seem to not be useable as
plug-ins to gimp-2.0.0, but that's not a problem for me.

I know pkgsrc can handle package dependencies on multiple versions of
the same libraries, but can this be extended to applications as well?
Could the above problems be eliminated by noting that one or another
version is already installed and modify the name appropriately?

E.g., if pkgsrc finds gimp-1.2.5 already installed (as /usr/pkg/bin/gimp),
then gimp-2.0.0 should be /usr/pkg/bin/gimp2, or similar and be left at
that, perhaps with a MESSAGE to that effect emitted by the build
machinery.  And vice-versa if it finds gimp2 already installed.

-- 
John D. Baker, KN5UKS                    NetBSD     Darwin/MacOS X
jdbaker(at)mylinuxisp(dot)com                 OpenBSD            FreeBSD
BSD -- It just sits there and _works_!