1) To totally remove, see the gmod/addons/ulx/cfg/server.ini ... there's an option there to disable it. When done, don't save over the original, save it to gmod/cfg
To edit it, make a text or html file called motd.txt and store it in /gmod/
2) Nothing to do with ULX (though ULX allows/has an rcon command.)
Please see google. Stands for remote console. You can use it to send commands to your dedicated server from your game.
