Is there any free available tool or X Window System tool like Exceed for Accessing the GUI of UNIX from LINUX/RHEL.
To access another system's desktop you can use either VNC (client and server) or you can use XRDP. XRDP is a wrapper that provides a layer similar to the remote desktop protocol (RDP) on Windows. To make connections to a system that's running the daemon (
xrdp) you can use one called
xfreerdp, there are of course others.