For GLib 2.25.5 GDBus D-Bus support was merged, providing an API to replace dbus-glib.
See http://library.gnome.org/devel/gio/unstable/gdbus.html and http://library.gnome.org/devel/gio/unstable/ch28.html .
According to a quick grep this module seems to use dbus-glib:
./at-spi2-core/configure.ac:PKG_CHECK_MODULES(DBUS_GLIB, [dbus-glib-1 >= 0.7.0])
Also applies to the atk part:
./at-spi2-atk/configure.ac:PKG_CHECK_MODULES(DBUS_GLIB, [dbus-glib-1 >= 0.7.0])
It seems a bit misleading to say that gdbus provides an API to "replace dbus-glib." Afaik it is a standalone libdbus implementation, so of course there is no equivalent to dbus_connection_setup_with_g_main, which is all I'm using dbus-glib for. The rest of my code uses libdbus, so am I required to rewrite it to use gdbus / is it now unacceptable for a module to depend on libdbus for GNOME 3.0? Feel free to point me to a relevant gnomegoal or similar.
Sorry, I don't code. Maybe http://mail.gnome.org/archives/commits-list/2010-May/msg03852.html helps to get an idea.
Round-trip calls are several times slower with gdbus than with libdbus from the testing that I've done. I've filed BGO#634471 for this. It would just not work for me to try to port AT-SPI to gdbus for this reason, and it would essentially mean *another* rewrite that I don't think I would have the time for right now.
That being said, AT-SPI is not really using the full dbus-glib API. It calls a total of two functions from dbus-glib (for main loop integration), and it is not clear that these functions were really meant to be deprecated except that they currently reside in dbus-glib. I've discussed the situation with people on #dbus and at the GNOME summit, and some people suggested that perhaps these functions should be put in a small library to be optionally built as part of the dbus module. I filed FDO#31515 with a patch to do this, but there doesn't seem to be a consensus as to what should be done. I could simply copy the code into libatspi if I needed to, as it isn't a large amount of code.
Depending on libdbus is OK for 3.0.