So I had a flick through the website, and I fail to understand how this service makes any money.

This automatically makes me suspicious that either they'll eventually start collecting data, or the service will disappear as soon as they are acquired.

At least they explicitly promote with "No profiling or data gathering" with a link to https://twitter.com/wire/status/768797320792117248

Also they promote Spotify

I seem to recall that they aim for a freemium-ish model, i.e. sell extra features or charge for features designed for businesses/teams etc.

Looks great, I was not aware they had open source client.

Given that they were forced to release their Axolotl (aka Signal protocol) under GPLv3+, they try to add some strange restrictions [2]:

"Additionally, if you choose to build an Open Source App, certain restrictions apply, as follows: a. You agree not to change the way the Open Source App connects and interacts with our servers ..."

As I understand I am free to ignore any additions to GPL.

[1] https://medium.com/@wireapp/axolotl-and-proteus-788519b186a7... [2] https://github.com/wireapp/wire

I read it as that only applies when you connect to their servers, and is the usage policy/Terms of Service for their servers, not a code license.

I also recommend Wire. I tried multiple alternatives for Skype and Wire was the only one which had good call quality and clients for all major platforms.