I found something that works for me.
First, I disable the standard (tinymce) editor for bbpress, with the following:
function my_bbp_use_wp_editor()
{
return false;
}
add_filter( 'bbp_use_wp_editor', 'my_bbp_enable_visual_editor' );
Then, manually replace the bbpress editor with ckeditor.
I did this at the bottom of ckeditor.config.js.
CKEDITOR.replace('bbp_topic_content', ckeditorSettings.configuration);
The bbpress editor replaces the bbpress editor, with the same toolbar configuration used in the comments.