[@robin-w Moderator 7 years, 9 months ago]

for

[bbp-subscribe-link forum_id=’557′]

this code (untested) should be close

function bp_subscribe_shortcode($attr) {	
//must have a forum_id or we just return !
  if (empty( $attr['forum_id'])) return	;
  else $args['forum_id'] = $attr['forum_id'];
  echo bbp_forum_subscription_link($args) ;
} 

add_shortcode( 'bbp-subscribe-link', 'bp_subscribe_shortcode' );