Yupp, copyright disclaimers are a good thing as its the first thing that makes companies angry when missing. Else so are GW not likely to bother unless they have plans to release their own editor, then they dont want competition, even if their own would also be free. But they have said that they dont plan to support the game, so they may have plans for a more hands off approach and thus might actualy encurage fan made stuff this time around.