BuddyPress.org

Here’s what I’m thinking in terms of user stories, assuming 2 groups (A and :

“I’m a user of Group A, so on the main blog, I see all Posts tagged A. I don’t see Posts tagged B.”

“I’m a user of Group B, so on the main blog, I see all Posts tagged B. I don’t see Posts tagged A.”

“I’m a user of Groups A and B, so on the main blog, I see all Posts tagged A and B.”

It will use blog tags, not blog categories.

It will support normal, private, and hidden forum types.

Assuming a post is tagged with A and B, the permissions are as expected:

“I’m a member of group A. I can see the post tagged A and B.”

“I’m a member of group B. I can see the post tagged A and B.”