I don't know how did it happen, but during make install I got:

-- Installing ./html/libgnomeui-gnome-vfs-util.html
-- Installing ./html/libgnomeui-gnome-window.html
-- Installing ./html/libgnomeui-gnometypebuiltins.html
-- Installing ./html/libgnomeui-objects.html
-- Installing ./html/miscellaneous.html
-- Installing ./html/index.sgml
/software/@sys/usr/bin/install: cannot stat `./html/index.sgml': No such
file or directory
make[3]: *** [install-data-local] Error 1
make[3]: Leaving directory
`/usr/local/scratch/libgnomeui-2.4.0.1/doc/reference'


Maybe this was related:

touch scan-build.stamp
*** Rebuilding template files ***
cd . && gtkdoc-mktmpl --module=libgnomeui
=============================================================================
WARNING: 19 unused declarations.
  These can be found in libgnomeui-unused.txt.
  They should be added to libgnomeui-sections.txt in the appropriate place.
=============================================================================
touch tmpl-build.stamp
*** Building SGML ***
cd . && \
gtkdoc-mkdb --module=libgnomeui --source-dir=../../libgnomeui
--main-sgml-file=libgnomeui-docs.sgml --output-format=xml
83% symbol docs coverage (763 symbols documented, 155 not documented)
See libgnomeui-undocumented.txt for a list of missing docs.
The doc coverage percentage doesn't include intro sections.
touch sgml-build.stamp
*** Building HTML ***
test -d ./html || mkdir ./html
cd ./html && gtkdoc-mkhtml libgnomeui ../libgnomeui-docs.sgml
warning: failed to load external entity
"file:///software/@sys/usr/share/xml/docbook/xsl-stylesheets-1.48/lib/lib.xsl"
compilation error: file
file:///software/@sys/usr/share/xml/docbook/xsl-stylesheets-1.48/html/docbook.xsl
line 25 element inc
lude
xsl:include : unable to load
file:///software/@sys/usr/share/xml/docbook/xsl-stylesheets-1.48/lib/lib.xsl