Why, oh why, has my Xnest gone away when upgraded to OSX 10.5? Not that I enjoy running X remotely, from my servers, but on occasion, it's required (thanks, stoopid Oracle and your sh*tty install routine).
If you want/need Xnest on your OSX Leopard desktop, you can accomplish it, this way:
First: Get Xcode: http://developer.apple.com/tools/download/
Second: install MacPorts: http://svn.macports.org/repository/macports/downloads/MacPorts-1.5.0/
Third: Install git, and development tools:
(from teminal window)
sudo port install pkgconfig automake autoconf libtool git-core
Install X.org libraries: (45 minutes)
(from terminal window)
sudo port install xorg-proto xorg-libX11 xorg-libxkbfile xorg-libXfont xorg-libfontenc
Forth: Get X server source from git and build it: see instructions on X.org wiki.
Fifth: Run configure as follows, NOT as how stated on X.org wikki:
./configure --prefix=/usr/X11 --enable-xnest=yes --with-mesa-source=`pwd`/../Mesa-6.5.2
Sixth: Continue with the rest of the source instructions as directed in the wiki page.
Seventh: Copy the new Xquartz binary over, then copy the Xnest binary as well:
sudo cp hw/xnest/Xnest /usr/X11/bin/
Eighth: Copy the manpage:
sudo cp hw/xnest/Xnest.1 /usr/share/man/man1/
That's it. Good luck. I suggest backing up, before doing the above.