The problem is not just an AGPL violation here, even though the license explicitly requires to show the code if you are providing a service on top of it. According to AGPL-3, if you are using the service you are the user. Good luck anyway submitting such a request to them at this point.
The actual problem is that #signal is no longer willing to publicly share the sources of their server platform, which is what #signalapp users criticized the most about others in the past, #telegram in particular.
@danielinux @Arcaik @mmu_man also, telegram had at least plausible explanation ("we were going to make server-side source code open from the start, but then we were tipped that a certain government is going to use them to set up their own surveilled messenger and block Telegram on its territory, so that people would not complain too loud because there is a government-managed alternative which is just as great but surveilled; and we had to scrap our plans").
I don't think there is any explanation from Signal?
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