I made a logo for free for this Minecraft server and they're scared of Copyright issues?

So, I made a free logo for a Minecraft server because I thought the change would be nice. He declined by saying that he doesn't feel comfortable because copyright issues may be involved. I don't understand.

I made this logo on Gimp and yes, it's mine, but I'm giving it to him, completely free. Is there a way I could make him know I intend not to put any type of Copyright on it? It's a simple graphic.

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