The custom oauth would obviously be used betweens sites that work together and are trusted.....like i have sites that use the invision community software and they have an oauth server but there is no module to allow for connect between UNA and invison....as an example.  Say i have my UNA site, and my friend has a site using a different community software.  We both want users to be able to login without having to create a whole new login, creating an SSO type situation....currently that can only be done between una/dolphin and the other major players