I’ve talked about group chatting with IRC, Slack, and Bindle, and recently stumbled upon Gitter.
The interface is a lot like Slack, but, unlike Slack, you can have public or private rooms (with the free plan private rooms are limited to 25 participants). Every user is required to have a Github account, and those accounts are also free. Gitter offers a web client in addition to clients for Mac, Windows, Linux, iOS, and Android.
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