It's easier to piggyback on something, for practicality reasons, and perhaps to piggyback on the perception people have of it (maliciously or not). ADDITIONAL

It's easier to piggyback on something, for practicality reasons, and perhaps to piggyback on the perception people have of it (maliciously or not). ADDITIONAL could simply mean added to, not necessarily extra or supplementary - added, as in, included with - an overlay of BSD. I agree, it'd be good if Facebook was more transparent as to what it all means. Stating that you'll believe it if they modify the actual BSD license, it's far more easy to take an existing - and generally accepted license - and then make an addition instead of making changes to it, no? So you don't have to call it something other than BSD?