Terry Hancock at FreeSoftware Magazine have blogged long and good about the issues between Debian and Creative Commons
Become smarter on the issue here
The problem essentially is this: none of the Creative Commons licenses have a “source” requirement (unlike the GPL, for example), because, being intended for creative content, it was generally felt that no definition of “source” was really workable, and what's worse, the intuitive rules for different media would likely be very different.
Because of this, there is no “parallel distribution” requirement for “source” and “binary” versions of works in CC licenses. Instead, the licenses insist on a much milder requirement: the work must be distributed in a form that at least does not actively interfere with the end user's freedom to use, modify and use, or distribute the modified version.
There has been a long-standing misconception that this provision would keep a user from applying TPM to a CC work in order to play it on a platform which requires TPM in order to play (a “TPM-Only Platform”). According to the CC representatives I've listened to, including General Counsel, Mia Garlick, this was not true in the previous CC licenses (that is: “yes you can TPM your own works on your own devices”). At the very least, the “fair use/fair dealing” provision is believed to provide this right in most jurisdictions, and the exact wording of the license is supposed to make it available generally. Nevertheless, there was agreement that the wording was too vague, and the CCPLv3 license has been revised to clear up the question (which I can vouch for myself, having read it — though, of course, unlike Garlick, I am not a lawyer!).
What Debian wants, however, is the ability to distribute packages in TPM form. They propose to obviate the concerns of TPM lock-in by requiring a parallel distribution of a non-TPM form of the work. This would be analogous to the way the GPL deals with source/binary distribution (in certain ways, binary distribution can be regarded as a kind of TPM distribution, since it is hard to reverse the binary to get usable source code for modifying the program).