[altimitmine]

I know this is old but I needed it to, so here is the answer for anyone else finding this on google:

1) Open bb-includes/functions.bb-meta.php

2) Find this line:

case 'url':

$option = 'uri';

3) After it, add:

case 'uri':

return "http://".$_SERVER['HTTP_HOST']."/forum/";

break;

Replace the “/forum/” part with the proper URL to your forums. For example

http://blah.com/bbpress/

would be:

return "http://".$_SERVER['HTTP_HOST']."/bbpress/";