I'm not sure if there are some entry requirements besides being interested but when I input my email I get the following error.
Missing admin scope: the token you provided is for an account that is not an admin. You must provide a token from an admin account in order to invite users through the slack api.
(it took like 200 attempts to read the error because it doesn't fit the button and just blinks when you attempt to sign on -_-)
Anyway I would be interested in joining your channel 