I don't know what the current status of the GtkGlArea project actually
is, however you can still grab gtkglarea from Gnome's anonymous ftp:
ftp.gnome.org. The latest version (1.99) does not work with my recent
Gtk2 installation. There is another GL support library for gtk2 with
which I have no problem: the Gtk GL Extension (the project seems more
active than the gtkglarea project, it also provides more
functionalities), you can get it at

   http://gtkglext.sourceforge.net/

If it helps, I have a straightforward ocaml bindings for part of this
library, you can get it at

http://gregory_guyomarch.imap-mail.com/code/ocaml-gtkglext-0.1.tar.gz

It has not been widely tested, but I have been using it for some time
and it works fine for me.

Regards,

Gregory.