This is probably partially in response to some of the issues that were discussed here: https://github.com/LibreSignal/LibreSignal/issues/37
Are there any recent counter examples of successful federated protocols?
It would be an interesting thought experiment to design a protocol that started with the basic features of IRC and incrementally layered on new features in backwards compatible / gracefully degrading ways until you arrived at Slack. Of course it would be a lot easier with the benefit of hindsight than if you started in the 1980s.
It's all that and more. Not only does it have the basic features of XMPP+IRC (and others), but it also federates/bridges with those existing open standards! Plus supports WebRTC signalling and of course end-to-end 1:1 & group encryption (Olm/MegOlm).
There's a range of client, server and library options. Vector.IM (with web, iOS and Android clients) is a good place for many to start and you can try on an existing service. Then if you want, just fire up your own server and it'll federate with the rest.
If you only needed pure XMPP, Conversations.IM is superb too.
[0] https://whispersystems.org/blog/the-ecosystem-is-moving/
Do you have an example of what you mean by "gag", in context of copyright?
Do you have an example of how GPL or other licenses allows you to do something negative while maintaining a positive image?
The GPL requires others to follow its terms, because that's the only license of the code that's available to them. There is no clause of the GPL or any software license that I'm aware of that prevents you from doing whatever you want with your own code under different terms.
Therefore, you can do something negative (sell software that uses changes to GPL'd code without providing those sources to others when they ask for it), while maintaining a positive image ("look, I license my code under the GPL because I care about software freedom").
You can see this happening in practice with software that has a "community" edition available under the GPL, but a paid version that's not GPL'd. The holder of the copyright gets to profit off of other people's well meaning contributions (which almost certainly will have had their copyright assigned to the original copyright holder), but the people who contributed don't get the benefit of the copyright holder's changes to that code that are only available to paid customers.
You can argue that those contributors made their contributions knowing that would happen, but the fact that it is possible somewhat undermines the entire point of the free software movement.
Is that the kind of gag that you're talking about, or did you mean something different?
I meant that the GPL as a license can be used to gag others while keeping a positive image as a person yourself. There are many licenses that can be used like this (the CDDL in particular was used for that purpose). That in itself has nothing to do with the GPL, more that you as a copyright holder have the ability to do things that are not available for others.
The GPL is a very good license, because it has one benefit that almost all other licenses don't: it restricts use of your code to free software. If you care about software freedom, or want to live in a world where proprietary software is a thing of the past, then that should be reason enough to use it. Positive image is not a clause in the GPL, so I really don't know what you mean.
If you don't like my software licensed under the GPL write your own damn software.