User accounts require registration with zoho??? Why???

User accounts require registration with zoho??? Why???

When I try to send an invite for a user to access my application it seems to require them to create a zoho account.  If so why? I dont want them to have anything to do with zoho.  They are my users and I dont want them to have to register with zoho. 

How can I get around this?  this is a deal killer for me if I cant get this to work.  I would gladly upgrade my account IF I can get features like this allowed.