According to this, Boric Anhydride is a form of boric acid.
http://www.reade.com/Products/Oxides/boron_oxide.html

it is a little lie. anhydride would be another name for boric oxide,
which mized with water would give boric acid. As we know, D76 contains
borax, whic is sodium tetraborate, iw. sodium salt of boric acid. In
formulations, you can use boric acid, or anhydride and required
quantity of sodium hydroxide. In my view, it is a deliberate
misleading statement by Kodak, to foul people.
Remember, MSDS are LEGAL documents to protect arses of manufactureres,
not any useful document for users. D76 formula was publish countless
times, it contains boraks.
Yes, borax is a salt of a weak acid and forms buffered solution.
Phosphates have differenet role to play.
Weaker developers may have system of borate+boric acid, which have
lower pH, ie. develop slower than D76.

*My favourite developer Kodak D-76 according to the material safety sheets
*contains a component called Boric Anhydride which at first I thought was
*just another name for Boric Acid until I read the CAS registry # is
*(1303-86-2) and the CAS # for Boric Acid is (10043-35-3).
*Does this component work in the same way as Boric Acid in that it helps to
*maintain a more stable pH? I also read that it is included with Microdol-X.
*It seems that ID11 is still made by Ilford to the original formula with the
*inclusion of Sodium Tripolyphosphate for use as a sequestering agent.
*