If the Debian project distributes the work and specifies license terms to the receiver, it doesn't matter who *wrote* those terms; it is the Debian project imposing the restrictions, by dint of distributing the software under those terms.
If Debian distribute a software; Debian may not impose any conditions whatsoever on a software he doesn't own the copyright. It is for this reason that Debian cannot sue somebody for violating the license of a software it distribute: because the license terms are imposed by the copyright holder, not by Debian. Debian can only give a copy (and usually is obliged to do so) of the original license term; specified by the original author. From the Debian point of view this is only for information: here is a software and here is the license terms that the original authors impose to you. (Some very permissive license might allow a distributor to sublicense the software; but it is certainly not the case of the GPL).
The GPL make the fact even more clear; the term of the license are imposed by the original author, not by Debian:
6. Each time you redistribute the Program (or any work based on the Program), the recipient automatically receives a license from the original licensor to copy, distribute or modify the Program subject to these terms and conditions. You may not impose any further restrictions on the recipients' exercise of the rights granted herein. You are not responsible for enforcing compliance by third parties to this License. Olive