[@johnjamesjacoby Keymaster 15 years, 8 months ago]

Create a page in your MU root blog called “forum” and leave it empty. Right now when the WordPress .htaccess file see’s a redirect to domain.com/forum/ it denies it saying the page doesn’t exist. Creating the page on your MU root blog will satisfy the .htaccess file, and still route to your bbPress installation.

Tricky eh?