> As I wrote under another comment, this doesn't seem like a good reason or I must be missing something because I can selfhost Matrix or an XMPP server and get notifications for free with any client.
I don't know about Matrix, but for XMPP, push notifications work like this:
XMPP Client tells the XMPP server where to send push notifications to (a server controlled by the client author); the XMPP server sends notifications there; the server connects with an API key to Google or Apple for the push notification to appear on your phone.
Presumably the cost of running a server is low enough that free Matrix and XMPP apps exist. It's definitely not free.
Zulip is charging to nudge businesses into using their paid version. It's their server that they are running, so they are free to do so. Your Matrix and/or XMPP client is choosing to not charge, which they are also free to do so.
Zulip provides instructions on how to use a different notification server; if you want to avoid giving them money that much, then you can do so.
I don't know about Matrix, but for XMPP, push notifications work like this:
XMPP Client tells the XMPP server where to send push notifications to (a server controlled by the client author); the XMPP server sends notifications there; the server connects with an API key to Google or Apple for the push notification to appear on your phone.
Presumably the cost of running a server is low enough that free Matrix and XMPP apps exist. It's definitely not free.
Zulip is charging to nudge businesses into using their paid version. It's their server that they are running, so they are free to do so. Your Matrix and/or XMPP client is choosing to not charge, which they are also free to do so.
Zulip provides instructions on how to use a different notification server; if you want to avoid giving them money that much, then you can do so.