BuddyPress.org

I haven’t tested this, but you should probably be able to edit

/wp-content/themes/buddypress-home/style.css

delete the @import directive that is there and instead add:

@import url(css/base.css);

@import url(css/custom.css);

This might hose some of the functionality added by loader.php, but should be the easiest place to make the change.