guacamole IS client-less in that it does not require a specific guacmole-client installed to the target in order to perform RDP, VNC, SSH or Telnet connections.
Some flavour of those services must however be installed/enabled/configured on the target host, be they supplied by the vendor (RDP with Microsoft say) or your choice (VNC on Linux say). I'd look towards VNC based connections over xRDP for *nix hosts personally. Ta, Carl
