If you have questions about using mojoPortal, you can post them here.
You may want to first review our site administration documentation to see if your question is answered there.
I set up a child site with related sites mode, so the users are shared between the sites.
But the openid/janrain/windows live authentication is not there, do i need to do a new registration and get new keys, or i can copy the parent site keys?
For host name based sites you would need a different account for each host name. For folder sites I think since it is the same domain you would use the same settings but I'm not sure it will work correctly or not.
Hope it helps,
Joe