The GNOME project is a lot of things. The following is taken from the GNOME FAQ, http://www.gnome.org/gnomefaq/html/x37.html
GNOME is the GUI desktop of the GNU Project.
To quote from the original announcement from comp.os.linux.announce, GNOME is intended
to be "a free and complete set of user friendly applications and desktop tools, similar
to CDE and KDE but based entirely on free software."
I, your lowly FAQ maintainer, like to explain GNOME as everything that's expected in a
modern programming environment. In this respect, it is approximately equivalent to CDE,
Win32, NextStep, or KDE. The big difference is that, unlike any of the above-mentioned
examples, every single component of GNOME is Free Software. Not only that, but GNOME is
extremely customizable compared to most desktop environments.
If all of this seems ambitious, that's because it is! Read on to find out more!
They don't have to be. Many popular window managers are not GNOME compliant, but because GNOME will probably be prevalent on *NIX desktops some day in the future, window managers wishing to provide as many features to users as possible should be GNOME compliant.
It must be noted that GNOME compliancy is always changing, and is not finalized whatsoever. Because of the pace of GNOME development, what worked one day, may not work the next. AfterStep is not 100% compliant, in fact, no window manager is. Some aspects of compliancy with GNOME cannot be implemented in AfterStep, because the window manager is much more powerful, virtual desktops and Pager, for example. Some window managers do a better job of compliancy than others. AfterStep attempts to be compliant in as many regards at it can, but perfection is not possible. If you are looking for a window manager that can run with GNOME almost all the time, and do it well, AfterStep is a good choice. If you want something that will cooperate with GNOME to the point of being GNOME, try something else.
The following are my (ishamael@themes.org) experiences with getting GNOME and AfterStep
running together like any other window manager. If you have any suggestions or other
ways to do this, please email me.
While in your current window manager (be it AfterStep or another):
Set the WINDOW_MANAGER variable to "afterstep" (in bash this can be done with 'export WINDOW_MANAGER="afterstep"' you should put this in your bashrc file.) Run "gnomecc" and go to the "Window Manager" section. "Add"
AfterStep is session managed, so check the box. At this point, save the settings, and close gnomecc (you might want to start it again and check it to make sure the addition is there).
You will also need to make a small change to the gnome-wm script (usually at /usr/bin/gnome-wm or /usr/local/bin/gnome-wm). The line that reads:
exec $WINDOW_MANAGER $*
exec $WINDOW_MANAGER
Now, you should close X down, and put "gnome-session" in your .xinitrc (or however you start X), and start it up again.
If all goes well, AfterStep and GNOME will start. Also please make sure you are using the Gnome AfterStep module, and a GNOME compliant feel (such as feel.GNOME).