The advertising clause is: "All advertising materials mentioning features or use of this software must display the following acknowledgement: This product includes software developed by the University of California, Berkeley and its contributors." If this causes problems, you can always elect to not mention the use of the software in advertising. That's annoying, but accepted. There's no such escape with front- and back-cover texts. It's also not at all obvious to me how accepting acknowledgements in advertising implies that this consession should be extended to everything else. Covers on a book? What next; is requiring that software pop up a dialog every fifteen minutes to say my name free? It's just this sort of wedging, saying "we allow this, so we should allow this, too--and wait, now we should allow this other thing too, it's just a little more!", that will destroy Debian as a free system. (And cover texts would not be a small concession at all, but a very big one.)
That is at least an elaborate argument. I personnaly think that Debian would do better to defend free software if there were in accordance to the FSF. Having DFSG-free and FSF-free software which are not the same just confuse the user and make the distinction between free / non-free less pertinent (a software won't be "non-free" anymore, it just will be non-XXX-free, where XXX is a small group of person). I still think that GFDL is not ideal and find curious that the FSF which have fighted the advertising clause of the original BSD license adopt a license where it demand even a little more. But I still think that Debian does more harm to the free software by purely rejecting the license. Debian have accepted as DFSG-free licenses which are, in my opinion, much more inconvenient that GFDL: I thing of the patch close of the DFSG4; although a software under this close can be modified, it is not clear if it is allowed to take a small part of the source code of a software under this license to incorporate in another work; whatever the license of this other work (the "trick" to have a huge patch which transform a software into another unrelated software will probable violates the license anyway: a judge might conceively decide that such a "patch" is not to be considered as a patch in the sense of the license).
Olive