All open source projects should offer an IRC channel, mailing lists and a forum!
And almost all do. Even newer ones like Elixir that started with Slack have now a mailing list and an IRC channel.
And almost all do. Even newer ones like Elixir that started with Slack have now a mailing list and an IRC channel.
Ideally those can be the same thing; see the current Mailman interface, or Discourse, both of which can provide a forum-like interface to a mailing list.
Forums are more for new and normal users/fans of open source projects. Technical discussions happen over IRC. And even more longer insightful technical discussions (often over several days) happen on mailing lists.