I think because Ubuntu is really in the "open source" camp they will use or
at least offer a proprietary program and both the free alternative if the
free alternative does not perform at a certain level (e.g. adobe flash and
gnash). Since open source only cares about the quality of software really if
the floss program doesn't meat a certain quality they will at least offer the
non-free program.
However, I believe if they are given two equal quality programs such as a
non-free rar unarchiver and a free one they will pick the floss one.
I mean if A and B are of equal quality but one is FLOSS and the other isn't
of course you would pick the FLOSS one even if you are in the open source
camp.
