MacOS – Is it possible to X forward from a mac

So if I am not mistaken the the problem you have with VNC currently is that it is sharing the current Mac user's screen with apps open that you don't want to see on your other computer? Lion introduces the ability to screen share users that are logged in the background. Quoting the text from the link:

• Enable Screen Sharing and set a VNC password.
• Take note of your computer’s IP address.
• Fire up a VNC client on another machine.
• Connect to your computer’s IP address along with the password you set earlier.
• You will see the Mac OS X login screen that appears when you first start the computer. If you log into the currently active user you will be controlling the computer’s screen. If you select a different user, you will be logged into that user’s desktop in the background. It will not affect what what is seen on the physical computer screen.

You will likely just need to create another user for sharing.

You can do it easily using ssh port forwarding. Open terminal and enter

ssh -L 5900:localhost:5900 remote_ip

with any other applicable settings you need. This will forward port 5900 on your local machine to port 5900 on the remote machine. If you need to change to a different local port (say, if you're already running a VNC server on your local machine), change the first 5900 to something else.

Then once the ssh connection is running, just VNC to localhost:5900, and you should get a connection to your remote machine.

If you don't have a VNC client already, there's one built in to Mac OS X. Open Finder, press ⌘K and enter vnc://localhost:5900 as shown below, and hit connect.