Django - Allow duplicate usernames
I'm facing the exact same problem and I've been reading a lot (about how to solve that problem in 1.5) and I just thought of a much simpler solution. What if you just add a fixed-length prefix with the organization id to store the username? 
I.e. Organization id = 115, chosen username = "john" and a fixed length of 6. So in the data base you store as username "000115_john".
When you do the login you just join the two parameters and try to authenticate with what Django provides. I'm not sure if the fixed length is strictly necessary but could avoid undesirable results if a user chooses a username with only numbers.
I'm working on a project in django which calls for having separate groups of users in their own username namespace.  
So for example, I might have multiple "organizations", and username should only have to be unique within that organization.
I know I can do this by using another model that contains a username/organization id, but that still leaves this useless (and required) field on the defualt django auth User that I would have to populate with something.
I've already written by own auth backend that authenticates a user against LDAP.  However, as I mentioned before, I am still stuck with the problem of how to populate / ignore the username field on the default django user.
Is there a way to drop the uniqueness constraint for the username for Django auth users?