Ubuntu has decided to address possible trademark issues by creating its own trademark policy.
Read more at eweek.com
Ubuntu's trademark policy opens by stating what's covered by the policy. “Canonical owns a number of trademarks and these include UBUNTU, KUBUNTU, EDUBUNTU, and XUBUNTU. The trademarks are registered in both word and logo form. Any mark ending with the letters UBUNTU or BUNTU is sufficiently similar to one or more of the trademarks that permission will be needed in order to use it.”