I'm running a Drupal 4.7.2 based website for a project. On this website, I created 3 roles of users and I approve/deny every single user that signs in.
Now, my boss asked me if it is possible that the user of a new partner's website (also in Drupal) can automatically become users of our site with their profile on the other site.
Is it possible? I want to keep this procedure safe and sound, how can I do it?



With drupal 5.0, definitely yes .. don't know about 4.x. You have two possibilities
The static way) you simply import the user list (http://drupal.org/project/user_import)
The dynamic way) You write a small module that hook the authentication:http://api.drupal.org/api/function/hook_auth/5 and hook the loading http://api.drupal.org/api/function/hook_user/5.

The procedures you described are for Drupal 5?

is this a one time merge or an ongoing sync of users between the two sites?

are you looking to move over user-created content (nodes or comments) from the other site into your site as well?

I still don't know. My boss is talking with this new "partner" of our and we are in a "feasibility study" phase, just making sure that things can be done.
I'll post more details when we come to a conclusion.