You can always use the Caffeine extension to stop the screen auto-locking.
For the latest versions of Gnome you are supposed to use dconf not gconf to change settings.
So to 'lockdown' the screen as @deusdara suggests, either run:
gsettings set org.gnome.desktop.lockdown disable-lock-screen true
Or navigate to org.gnome.desktop.lockdown in dconf-editor and tick disable-lock-screen
The problem with this (I ain't checked much), is that this may only remove the 'lock' button from the menu, but it is still lockable via the keyboard shortcu, so it might still lock automatically.
Apart from the other suggested methods, there is always this:
sudo yum remove gnome-screensaver 
Surprisingly, this does not remove half the system as dependencies... But still is not much of an idea.
The top two ideas tested in Gnome 3.8.4 on Fedora 19 - Caffeine works brilliantly, while the second one vaguely works
Here, there are no icons on the desktop without special effort. What version of Fedora are you using?
randomuser ( 2013-11-27 03:50:40 +0000 )editUm.. Yeah. Turns out I don't have icons on the Desktop :D. I'm a bit distracted as a person and usually I don't pay attention to things. When I posted this, I had. Now I don't have (it's been a couple of days) and when I think about it, I didn't have except for that time. Not sure why is that. I still can't disable the lock screen though
P.S. Thanks for the edit on the question
Kalo Stoyanov ( 2013-11-28 13:19:48 +0000 )editWhich version of GNOME are you using?
wilf ( 2013-12-01 23:58:28 +0000 )editI'm using 3.8
Kalo Stoyanov ( 2013-12-03 19:18:39 +0000 )edit