Description of problem: gdm dont start if gnome-session is not installed How reproducible: install gdm without gnome-session (XFCE Live-CD)
GDM and gnome-session shared a lot of duplicate functionality, so in the last release Jon rewrote gnome-session to be general enough to be leveraged by GDM and removed the duplicate code from GDM. GDM needs it to work. Is gnome-session pulling in other deps you don't want? or is it just gnome-session?
We've made gdm require gnome-session