The Ubuntu Community Council has issued a very interesting statement
The Ubuntu Community Council has issued an official explanation for the reason why Linux Mint developers have to sign a license agreement in order to continue to distribute the package straight from the Ubuntu repos.A while ago, during a dispute regarding the security of the Linux Mint operating system, the project leader said a very interesting thing, which had no follow up until now.
“I personally talked to the legal dept. at Canonical (for other reasons, they’re telling us we need a license to use their binary packages) and it is clear they are confused about LMDE and Mint. They don’t know what repositories we’re using and they don’t know what we’re doing,” said Clement Lefebvre.
A few months later, Ubuntu Community Council has decided to issue a statement that clarifies this issue, explaining why developers need to sign a license agreement.
“We believe there is no ill-will against Linux Mint, from either the Ubuntu community or Canonical and that Canonical does not intend to prevent them from continuing their work, and that this license is to help ensure that. What Linux Mint does is appreciated, and we want to see them succeed.”
“At this time, we are in agreement that one of the keys to Ubuntu’s success is in providing a well-designed, reliable and enjoyable experience to all of our users, whether they are using Ubuntu on a desktop, a phone or in the cloud. To that end it is critical that when people see ‘Ubuntu,’ it adequately represents the software that we all build and stand behind,” says the communique from Ubuntu Community Council.
In short, Canonical has the right for the Ubuntu trademark and everything that goes with it. It is required to protect those trademarks in order to keep them. It sounds weird, but that's actually a very important rule.
Moreover, even Ubuntu and all of its flavors have a license for the use of the protected trademarks, and this speaks volumes about how serious the company is about those trademarks.
Update - As pointed out by one of our readers, Ubuntu Community Council is not Canonical, and you should bear that in mind, Nonetheless, the idea and message of this statement doesn't change, not the obligations of other distributions that are using the Ubuntu repositories.