The only form of external userbase support that our Cloud (formerly OnDemand) JIRA and Confluence support at the moment is sourcing the userbase (and authenticating users against) Google Apps. Docs are at Managing Users and Groups with Google Apps.
However, technically, at the other side, Crowd supports being the SSO provider for Google Apps (documentation: Crowd's Configuring the Google Apps Connector).
In theory, it's possible that in this way you could get Cloud JIRA and Confluence to talk to Server Crowd (i.e. that you host) via Google Apps, but I haven't heard of any customer going down this path; you'd probably be "swimming upstream", to say the least.
Typically people who go down this line of reasoning want to connect to their Server Crowd in order to expose users from their LDAP server to our Cloud products; if that's your situation, you may like to vote on AOD-1837 - Support LDAP integration with OnDemand.
Hello Atlassian Community! I'm Teresa, the Product Marketing Manager for Jira Service Desk Server at Atlassian. I'm excited to announce two exciting releases for Jira Service De...
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG
You're one step closer to meeting fellow Atlassian users at your local meet up. Learn more about AUGs