OK, I see both the server and the client software are released with a #FreeSofteware license (GPL, AGPL). I read https://wire.com/en/legal/ which acknowledges the "Open Source App", which doesn't give any info on server source code (although it does mention that connecting the Open Source App to non-Wire services is allowed, and removes some restrictions from the Terms). Those ToU sure seem non-free to me, tho.