A few choice snippets from the GPLv3 license:
You may not propagate or modify a covered work except as expressly provided under this License. Any attempt otherwise to propagate or modify it is void, and will automatically terminate your rights under this License (including any patent licenses granted under the third paragraph of section 11).
Each time you convey a covered work, the recipient automatically receives a license from the original licensors, to run, modify and propagate that work, subject to this License.
And this last one is a doozy. Are you ready? Brace yourselves:
You may not impose any further restrictions on the exercise of the rights granted or affirmed under this License. For example, you may not impose a license fee, royalty, or other charge for exercise of rights granted under this License, and you may not initiate litigation (including a cross-claim or counterclaim in a lawsuit) alleging that any patent claim is infringed by making, using, selling, offering for sale, or importing the Program or any portion of it.
This applies to both binaries and source code. So in fact, by attempting to enforce some external licensing terms on Mint, for GPLv3-licensed software (which is plentiful in the Ubuntu repos), Canonical is in fact in violation of the GPLv3 license. I have to check if v2 contains similar clauses, but I suspect it does. With this in mind, Canonical could actually lose the legal right to distribute GPL-licensed software, which would shut down the repositories for good, if the copyright holders were to complain...
(Note that the GPL license explicitly does allow charging money from the recipient of a software, either binary or source code. It does not however allow dictating what the recipient is allowed to do with the software or how they're allowed to use it, apart from the terms outlined in the GPL license itself.)
edit. GPL version 2 contains this:
4. You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense or distribute the Program is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.
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.
So according to this, Canonical would be violating both the GPLv2 and GPLv3 if they were to attempt to dictate how Mint is allowed to use the GPLv2 or GPLv3 -licensed binaries in their repositories. Canonical is allowed to charge a fee for those binaries, but not dictate how Mint can use those binaries.
Clem himself said: "The licensing aims at restricting what Mint can and cannot do
, mostly in relation to the OEM market, to prevent Mint from competing with Canonical in front of the same commercial partners." So I don't see anything unclear about this, that is obviously a GPL violation. Canonical is walking on thin ice here, they should seriously fire their lawyers for putting them in such a risk... this thing seriously threatens the future of Canonical and Ubuntu. If a copyright holder complains about the violation, Canonical can no longer legally distribute the software, and that'll shut down the entire distro for good. (And by extension Mint, at least in it's current, Ubuntu-derived form).