I think it's okay to replace the logo with your own. I have seen many people do it and I myself did it after taking permission from Thomas, so I guess this is not a violation of the license.

On 9/24/06, Kenn Murrah <kennmurrah@gmail.com> wrote:
Pardon the elementary question, but is it permissible to replace the RoundCube logo with a company logo?  I'm not sure how the license views this, and I don't want to do inadvertently violate the license.

thanks.