[maka]

You can change anything you want to server side with RunUO, but you cannot change lets say the graphics. If i wanted to add new hot keys in the client I couldn't change that through RunUO either. Not sure if you understand the examples, they are not particularity good, but I cannot explain the benefits of having the client source in an easy way:/

Having the client source, I could make a new game based on UO, just using RunUO I couldn't do that. I can't add "features" that are not in the client already cause the client "speaks" with RunUO.

For example, I could program a voice chat server with RunUO, but if I sent "voice" to the client, the client wouldn't know what to do with it.