It is advisable to try the pre-compiled package for your distribution before you try to make GNOME Power Manager from source.
You can check out the latest GNOME Power Manager code using SVN. You can use the viewcvs interface too.
svn checkout http://svn.gnome.org/svn/gnome-power-manager/trunk/ gnome-power-manager-trunk
To compile and make, use the following procedure:
cd gnome-power-manager ./autogen.sh --prefix=/home/hughsie/root --enable-applets --with-gconf-source=xml::/home/hughsie/.gconf make make install