A closer equivalent would be riot.im's servers, which are free in the same way as Discord/IRC's public rooms are. If you wanted custom integrations or the like you'd have to pay out for it, but the free option's still there. You can find a decent number of communities there--#GnuLinuxLovers comes to mind.

I should also say that Matrix has a lot of other really nice aspects to it that give Discord and friends a run for their money:

- Open source. Self-explanatory.

- Federated. Sure, you can probably redundant-ify your IRC server with Apache Something and Amazon AWS/ Cloudflare whatever if you really wanted to, but I regularly see Matrix rooms with 10+ addresses because the protocol's designed around that redundancy, not the other way around. And of course with Discord none of this even applies...good luck if Intern Greg elbows the Big Red Button, or they pull a yahoo groups/google+/etc.

- The protocol leaves a lot of room for experimentation that Discord isn't nearly open enough for. [1][2][3]

- There's bridges to other discord, irc, and dozens of other platforms, sidestepping the adoption problem (note that there's been even more added since this graphic was made). [4]

They aren't exactly languishing in obscurity either: the government of France is one of their userbases [5]. Yeah, I'd say Discord-style VC would be nice, but the lack if it isn't exactly holding them back.

[1]: https://matrix.org/docs/projects/other/matrix-live/ [2]: https://matrix.org/docs/projects/other/freebird/ [3]: https://matrix.org/docs/projects/other/lightrix/ [4]: https://matrix.org/blog/2017/03/11/how-do-i-bridge-thee-let-... [5]: https://vector.im/#case-studies

I'm not a fan of paying per user, but the usage is only counted towards the billing when they stick around for two days. That makes it a better deal than if you were charged per invite.

Oh, sorry, I didn't know Discord gives people their own exclusive servers to host their rooms on for free. I assumed you just create new rooms on their main server, in which case it would be comparable to signing up to the matrix.org homeserver for free and create as many rooms there and invite as many users to those rooms as you want.

That's only if you want your own server. If you just want a room for you and your friends, you can use the primary instance for free (you can make private rooms too, if that takes your fancy).

The only thing this doesn't let you do is install bridges to other services (such as Discord). For that you'll need your own server.

Voice chat is apparently harder to implement, but it's still possible to do right now with Jitsi [1]. And even without it, Matrix supports an 'opt-in' style of voice channel that should work fine with smaller groups.

[1]: https://github.com/matrix-org/synapse/issues/6471

For the chat there is weechat, but I do not think any of lightweight the clients with audio support are mature.

If you want a _really_ lightweight matrix client, I'd say <300 lines of Go would be pretty light. Go is quite portable too:

https://gitlab.com/meutraa/mm/tree/master