now the zenphoto system is only for single user or specific users. can you guys add the function for user register freely? and user can manage their own albums, just similar as flickr.

There are no plans for this. You could submit a ticket with a new feature request if you wish. However it is unlikely that this will make it to the top of our priority list.

In the mean time, you have almost this functionality. You just have to create the users yourself and give them the appropriate album and rights.