In Debian's case at least, I don't think there's an objection to third-party projects or forks using names derived from the name "Debian", so long as they aren't actually identically the name "Debian". For example, there is a distribution called "Illumian" which is made up of the Illumos base OS and a Debian-derived userspace.

Besides, I don't really see a trademark issue here. The term "cdr" preexists both of the projects, and is owned by neither of them. A person named their software after a fairly generic derivative of this term, "cdrtools". And now they are complaining that someone else named their software a different generic derivative, "cdrkit"? Do they claim that nobody else should be able to use the prefix "cdr" followed by a noun? Given that they did not even invent the prefix "cdr", that seems like quit a stretch. That's like someone who named their backup product "Backup Tool" complaining that a different product is named "Backup Kit". Sorry, but you don't own the word "backup".