BuddyPress.org

Each group has the option to have an associated forum.
Groups can be public, private or hidden.
There can also be site-wide or ‘general’ forums.

Forums require the use of an additional plugin: bbPress.

I also want people who are workshop leaders to be able to see and post to any forum.

You make them members of all groups.
If you’d rather not, then you’ll need to write some custom code.

For option 1 it sounds like you want to set up a private network – not allowing non-logged in users to view profile details etc.

There’s a few options as to how to go about this, here’s a few:

http://buddyuser.com/category/plugin-review/private-network

For option 2, one option might be to display the registration form in a widget area on the front page, it’s possible to only display this widget for logged out users:

http://buddyuser.com/plugin-review-buddy-registration-widget

Thank you so much for this code! I’ve spent several hours trying to use other people’s code to hide the button and even tried to make my own but nothing worked until I found your code. I just switched it around because I only wanted one particular group to not be able to send messages while the rest can.

Posting in case someone in the future needs the opposite of your code:

add_filter( 'bp_get_send_message_button', function( $array ) {
    if ( pmpro_hasMembershipLevel('NAMEOFPMPLEVEL') ) {
        return '';
    } else {
        return $array;
    }
} );

Also, I am looking for the same code as you to restrict non-paying users from sending private messages. I found a code that looks promising but unfortunately doesn’t work. It sees if the user is logged in and if not redirects them. Then if the person is logged in it checks their role but if they’re not that role they’re supposed to be redirected. But it just breaks my whole site. Any ideas?

function my_function() {

    if ( ! is_user_logged_in() && bp_is_current_component( 'messages' ) ) {
        // Current user is not logged in so don't let them see stuff. In this case, private messages 
        wp_redirect( home_url() );
        exit;
    }
        
    $flag = false;
    // Get current user info.
    $user = wp_get_current_user();

    if ( ! in_array( 'student', $user->roles ) ) {
        // The current member is not a student.
        $flag = true;
    }

    if ( $flag && bp_is_current_component( 'messages' )  ) {
        The currently logged-in member is not a student and is trying to view private messaging. Let's redirect them away.
        wp_redirect( home_url() );
        exit;
    }
}
add_action( 'init', 'my_function' );

Have you tried setting the forum to Private? Or Hidden?
Go to wp-admin > Forums > Forum Name > Edit > Visibility

btw – these are the BuddyPress forums.
For support for bbPress you should use their forums.

There’s a few plugins that do that but BP Registration Options allows you to set it as a private network, in BP Registration>>BP Registration

I asked seventhqueen for help and they said the problem is from buddypress, they can not help.

When you have a private group and go to approve some member the warning is showed but after approving, when the page reload saying that the membership was approved, the warning dissapears, is the only page where the warning is not being showed.

Set it as a private network?

This works and hides the button, but I’m curious. Can someone still send a private message to another user when they are “not” friends using URL manipulation or should the _wpnonce stop that?

It could be, difficult to answer since you have not given a great deal of detail on what features you want. You can create multiple extra profile fields which are searchable, you can use a plugin like BP Profile Search to enable all sections of the profile to be searchable, and of course BP supports public and private forums.