I think of "worksafe" as the most restricted category; there's plenty of content that's considered reasonable in public that's inappropriate in an office (which is what "work" mostly means in this context--nobody means "okay for viewing by construction crews," much less "wouldn't offend strippers on the runway").
"Worksafe" doesn't, in my mind, mean "legal." Legal's much broader. So's "acceptable in public." Work is supposed to be an offense-free environment, one that is more restricted in communication & attitudes than the general public.
But I'm much more concerned with the concepts of each of the four levels, than the label used for them; I'm hoping that, by opening the discussion and finding some words that don't label the reader, others will throw vocabulary at me until, by some fannish osmotic consensus process, the magic "right words" will become apparent to everyone.
Or at least to me, and then I can pester everyone until they start using them.