Note that one of the projects on this list - Element - recently changed their license to one intended to make it impractical to deploy the open source version and make users buy commercial proprietary licences instead for the specific reason that governments were buying support for their software from companies other than them and they wanted to stop that. Which I think shows a pretty big practical limitation of this approach.
The AGPLv3 is designed to ban versions with proprietary alternations full stop. In order to do that, it places some pretty daunting requirements on any modification - even open source ones. The moment you make any change, you must ensure that all users interacting with the software over the network are offered an opportunity to receive the corresponding source and that offer must be prominent. The original software does not have to include a way to offer such notices, just updating any existing code that does to point to the modified source is not necessarily sufficient to comply (unlike with the previous Affero GPL), and the protocols it relies on don't even have to be designed in a way that makes this feasible. It's not clear how this would even work with a federated chat protocol.
> The original software does not have to include a way to offer such notices, just updating any existing code that does to point to the modified source is not necessarily sufficient to comply
This is not what the license says.
"If the work has interactive user interfaces, each must display Appropriate Legal Notices; however, if the Program has interactive interfaces that do not display Appropriate Legal Notices, your work need not make them do so." https://www.gnu.org/licenses/agpl-3.0.en.html
That's a clause from the standard GPLv3 covering something different:
"An interactive user interface displays “Appropriate Legal Notices” to the extent that it includes a convenient and prominently visible feature that (1) displays an appropriate copyright notice, and (2) tells the user that there is no warranty for the work (except to the extent that warranties are provided), that licensees may convey the work under this License, and how to view a copy of this License. If the interface presents a list of user commands or options, such as a menu, a prominent item in the list meets this criterion."
The requirement to offer users of modified versions interacting remotely over a computer network a copy of the source is seperate and has no such limitation. Which rather suggests that the drafters of the license considered this issue of requiring people to make unrelated modifications and did nothing to stop it.
