[Hephos]

You can always get rid of the ads if you are picky about it by purchasing the license. Basically the free version with ads is for people to be able to use the client when they cannot afford the license. They can build their custom client and if it turns out to be great, they can pay the license if they want to. And any serious mud that want an own custom client should have no problem purchasing the license. The fee is low compared to ordinary similar software licenses.

Most mud clients have ads more or less in them from scratch with icons or 'existing' setups for muds. Take zmud for example. The first thing you see is a button to connect to another mud when you start it. Most muds also have big voting buttons on their front pages sending the players to sites like this that are litterally pulsating with rival muds.
Some large muds even post ads for other muds/games on their own website.

With scapefx your players won't even be able to connect to another mud from within the client. (Like almost any other client would allow them). When you start the client it will only connect to your mud. The banners will take the players to their websites, just like these sites do.