See http://live.gnome.org/GnomeGoals/RemoveLibGladeUseGtkBuilder .
Filing as Evolution uses libgnomecanvas.

Grepping for "glade" in libgnomecanvas:

./glade/glade-canvas.c: * libglade - a library for building interfaces from XML
files at runtime
./glade/glade-canvas.c: * glade-canvas.c: support for canvas widgets in
libglade.
./glade/glade-canvas.c:#include <glade/glade-init.h>
./glade/glade-canvas.c:#include <glade/glade-build.h>
./glade/glade-canvas.c:glade_module_register_widgets (void)
./glade/glade-canvas.c:    glade_register_custom_prop (GNOME_TYPE_CANVAS,
"anti_aliased", set_aa);
./glade/glade-canvas.c:    glade_register_custom_prop (GNOME_TYPE_CANVAS,
"scroll_x1", set_scroll_x1);
./glade/glade-canvas.c:    glade_register_custom_prop (GNOME_TYPE_CANVAS,
"scroll_y1", set_scroll_y1);
./glade/glade-canvas.c:    glade_register_custom_prop (GNOME_TYPE_CANVAS,
"scroll_x2", set_scroll_x2);
./glade/glade-canvas.c:    glade_register_custom_prop (GNOME_TYPE_CANVAS,
"scroll_y2", set_scroll_y2);
./glade/glade-canvas.c:    glade_register_custom_prop (GNOME_TYPE_CANVAS,
"pixels_per_unit", set_pixels_per_unit);
./glade/glade-canvas.c:    glade_register_widget (GNOME_TYPE_CANVAS,
glade_standard_build_widget, NULL, NULL);
./glade/glade-canvas.c:    glade_provide ("canvas");
./glade/Makefile.am:glademoduledir = $(libdir)/libglade/2.0
./glade/Makefile.am:glademodule_LTLIBRARIES = libcanvas.la
./glade/Makefile.am:    glade-canvas.c
./Makefile.am:SUBDIRS = libgnomecanvas glade demos po tests docs
./libgnomecanvas-zip.in:lib/libglade/2.0/libcanvas.dll
./libgnomecanvas-zip.in:lib/libglade/2.0/libcanvas.dll.a
./configure.in:m4_define([libglade_required_version], [2.0.0])
./configure.in:PKG_CHECK_MODULES(CANVAS_GLADE, $CANVAS_MODULES libglade-2.0 >=
libglade_required_version)
./configure.in:glade/Makefile
./po/POTFILES.skip:tests/test-libglade-canvas.glade
./tests/Makefile.am:    test-libglade-canvas
./tests/Makefile.am:   
LIBGLADE_MODULE_PATH="$(top_builddir)/glade/.libs:$(LIBGLADE_MODULE_PATH)"
./tests/Makefile.am:    -DGLADEFILE=\""$(srcdir)/test-libglade-canvas.glade"\"
./tests/Makefile.am:test_libglade_canvas_SOURCE = test-libglade-canvas.c
./tests/Makefile.am:EXTRA_DIST = test-libglade-canvas.glade
./tests/test-libglade-canvas.c:#include <glade/glade-xml.h>
./tests/test-libglade-canvas.c: xml = glade_xml_new (GLADEFILE, NULL, NULL);
./tests/test-libglade-canvas.c:         toplevel = glade_xml_get_widget (xml,
"window1");
./tests/test-libglade-canvas.glade:<!DOCTYPE glade-interface SYSTEM
"http://glade.gnome.org/glade-2.0.dtd" >
./tests/test-libglade-canvas.glade:<glade-interface>
./tests/test-libglade-canvas.glade:</glade-interface>