Hallo,
I just stumbled accros this: http://www.debian.org/legal/licenses/dls-006-ccby
It's interesting why debian-legal sees CC-By as "non-free". Quote:
Summary: non-free Restricts modification Justification:
* It appears (though it's slightly unclear) that credit to original author(s) must be as prominently displayed, and in the same location, as credit to any other author. This restricts modification (DFSG §3). * When any Licensor asks, all references to their name(s) must be purged from the work. This restricts modification (DFSG §3). * Use of the "Creative Commons" trademark (or related trademark or logo) appears to be a license violation, and thus grounds for a copyright holder to revoke the license. This violates the "Tentacles of Evil" test and can remove all freedoms the license grants.
This references the trademark notice on the license's website where it is not obvious if this notice is part of the license.
I think, especially the trademark issue is noteworthy.
Ciao