Who was Guillaume Maran?

For an authoritative answer, I contacted the professor of history at the University of Toulouse, Jacques Krynen, who has written a biography of Guillaume Maran. His response [*] to the puzzling inscription on Maran's statue in de Salles des Illustres strengthens the case that it was an error. My (unsubstantiated) guess is that this happened when the 17th century statues were reconstructed in 1892 after having been destroyed by a fire a few years earlier (as described here).

[*] Il y a bien longtemps que je ne me suis pas rendu salle des illustres... en tout état de cause Guillaume Maran était professeur de droit. Pas mathématicien! (I have not been to the hall of celebrities for quite some time... in any case, Guillaume Maran was professor of law. No mathematician!)

Guillaume Maran was a lawyer but not a mathematician. See this page from the Bibliotheque nationale de France for some of his work.

But there should be a mathematician/physicist/theologian bust in the gallery: Emmanuel Maignan. The presence of the bust is mentioned in that source and in the book mentioned by Fedja.

So may be the similarity of the names of the two great men have contributed to attributing the virtues of one to the other.

The "minimes" was a particular religious order that existed at the time, and is frequently mentioned in 17th century sources. It seems that he was a religious authority (prieur is somewhat less than an abbé (abbot) for the order.