The text in the middle circle reads:
¶ Leslettres de ci environ¶ Si font le non & le surnon¶ Qui bien les saroit a droitmetre ¶ Et curieux de l'entremetre ¶ De celui qui cest livrefist ¶ Et du clerc qui son songeescripst ¶ Qui la prophecie amoustre ¶ U cercle des-sus est nomme ¶ Quile livre a fait &
Which may be translated as:
The letters here about
Make the name and the surname
To whomever can put them in the right order
And is curious enough to try
Of he who made this book
And the clerk who wrote his dream
That showed the prophecy
Is named in the circle above,
Who made and found the book
and around them in plain brown ink the letters: DRHIENREIESEREF
A link to the original full-page image on Gallica:
The 15 plain brown ink letters DRHIENREIESEREF can be rearranged to form the name "Henri de Ferrières", but if this is the correct decipherment, the scrambling of letters does not seem to have been done according to any regular or logical system, meaning that it is of no help in unscrambling the other name.
From the 12 red letters HDOSEDMISNER we could make a three-part name with "de" in the middle, but the absence of the letter "a" means we cannot make several common fore-names such as JEAN/JEHAN.
HENRI is possible, which leaves the letters DOSEDMS (with just two vowels.)
RENE is possible, which leaves the letters HDOSDMIS
SIMON is possible, which leaves the letters HDSEDER
... and so on.
Alphonse Chassant, who first decrypted the author's name in the Bulletin de bouquiniste (1869), suggested that the scribe's name could be decrypted as "Denis d'Hormes", and backed-up this suggestion by citing various documents connecting the Ferrières and d'Ormes families; for example, before 1348, a Félice d'Ormes was the widow of an Henri de Ferrières.
For a full discussion of the authorship and interpretation of the colophon, see Artur Gunnar Tilander (ed.), Les Livres du Roy Modus et de la Royne Ratio, Société des Anciens Textes Français (2 vols. Paris, 1932), I, pp.L–LIV.