[e12e]

Isn't this a bit like saying: if it's for issue tracking, there's Bugzilla/trac/issuetracker/phabric, or if you need a wiki there's moinmon/mediawiki, or if you need a blog there's ghost/wordpress ?

More to the point: IRC (out-of-the-box) doesn't do archiving/search. Slack isn't self-host (which isn't an issue with people using github -- but it does introduce another vendor). Using external services forces you to maintain group membership, user-meta-data either in different user-databases, or via some form of federation.

No longer is removing a user/ssh-key from a github project enough to plug a hole in case of a hacked account.

Discourse isn't (that) bad -- but mailinglists are a lot better IMNHO. If you have a half-decent email program, like mutt, or even (al)pine.

At any rate, the ability to work via email (get bugs via email, close bugs via email) leverage what email is good at: off-line+synchronization. Which is one of the things git is good for. You know, distributed work.

[e12e]

Well, re: authentication -- I didn't think to check slack's support for oauth etc... apparently there's 0auth.com:

https://slack.zendesk.com/hc/en-us/articles/203772216-Using-...

https://auth0.com/docs/identityproviders

Not sure about authorization and group membership, channel authorization etc -- I assume you'll need to manage slack authorization with slack, and github authorization on the github side.

But fair's fair.

[ed: And now you have three providers:

https://auth0.com/pricing ]