I'm the last person to defend lawyers, DMCA takedowns, etc. But Signal has very strict build processes in place to ensure (to the best of their ability, anyway) that the official binaries are devoid of side-channel attack vulnerabilities.
Putting my tinfoil hat on, all it takes is one unofficial Snap maintainer to be approached by one Glow-In-The-Dark with an offer they can't refuse to infect a hundred thousand users with key material compromise.
I hate to say it, but Signal is doing the right thing, here.
Read the full context of that rule. The entire section allows those provisions to be applied, it does not make those provisions. The APGLv3 disallows any further restrictions beyond the license to be applied, except for a handful of exceptions. That's one of them. And if such an exception is made, further instructions are provided to inform downstream users of them. Signal did not follow those instructions and didn't make any of the permitted exceptions.
Signal’s Rights. We own all copyrights, trademarks, domains, logos, trade dress, trade secrets, patents, and other intellectual property rights associated with our Services. You may not use our copyrights, trademarks, domains, logos, trade dress, patents, and other intellectual property rights unless you have our written permission. To report copyright, trademark, or other intellectual property infringement, please contact abuse@signal.org.
They own it, sure, but they license it out freely. They've released their work under a license that allows anyone use of their trademark, as long as they stick by the AGPLv3. The AGPLv3 is written permission.
I think what Signal is objecting to is that the snap looked like it was packaged and distributed by Signal when the files included could have been modified with a backdoor or whatever.
