The developers of GhostBSD have chosen to take a new direction with their desktop-oriented operating system. They have abandoned all desktop environments, including GNOME, to take on MATE. The desktop environment MATE is an offshoot of GNOME 2 featuring large improvements. You can try out MATE on GhostBSD 3.5. Version 4.0 is currently in the works and will feature MATE only.
Check out the full announcement at: http://ghostbsd.org/node/197