Difference from CCK Field Privacy?

Main difference: CCK Private Fields stores privacy settings for fields at node revision level, and it supports integration with Diff. This is not possible with CCK Fields Privacy.

Also, here we have global permissions that allow, not only the node author, but other users edit privacy settings, or view private data. But the granularity of these global permissions is at field level. ie. "view private data for field %field_name" and "edit privacy options for field %field_name".

I described these features in the project page, but maybe I should describe more clearly these basic differences there?

Sure, no problem. I fully understand these concerns. I think I try to avoid adding clutter to the modules repository, even though sometimes this is not easy. Time to develop means money, and we should try to avoid increaing the cost of our projects, when possible. Sometimes is also easy to write your own than trying to spend time on something that you already see it will cost you more, or maybe what you need is not fully compatible with the features of something that already exists.

This time, I analyzed CCK Field Privacy before starting to work on this one. I need the above mentioned features for the project I'm working on, I also need the module is as optimized as possible.

I guess both modules may cover different use-cases.

Another difference is that the hook this module uses to check for "Private" access has the node as argument, and this allows custom modules use node data to grant/deny permissions to view each field. I think I also covered this in the API section of the README.

Please, let me know if there's something I can add/change to the project page, so it's easier to see the differences.

Good idea. Thanks for asking. :)

Should these modules be merged?
Posted this question in the other queue too:
http://drupal.org/node/918366