Does anyone know if there are there any GPL equivalents to this 
commercial product?
http://www.thinstuff.com/products/lx-server/
( a multi-user X server combined with an RDP (remote desktop) server )
I want to give (Windows) desktop users access to a remote copy of the 
Firefox web browser running on a firewalled and sandboxed Linux server. 
  Basically I need a multi-user X server combined with a VNC or RDP 
server.  I don't want a whole remote Linux desktop, just a remote 
Firefox window for several users.
Simon