Is the VM an autograph or copy?

[MarcoP]

Taking everything we know about the imagery into consideration, I would personally think that it is a unique work adapting numerous sources. 

This is close to my point of view, maybe with the difference that I find "adapting" too strong. Overall, we have been unable to find any single source that we can reliably say was "adapted" into the VMS. Possibly, the closest we get is the oak-and-ivy illustration in Manfredus BNF Lat 6823. Is that enough to say that the Tractatus De Herbis was adapted into the Voynich herbal?

Art historians like Toresella and Touwaide have pointed out that the author was aware of the visual tradition of Western herbals.
Ewa Sniezynska-Stolot first pointed out that the zodiac shows a connection with zodiac cycles produced in Central Europe.

We can be sure that the author had seen herbal manuscripts and zodiac cycles; familiarity with illustrated balneological treaties like De Balneis Puteolanis is also likely. He was certainly inspired by other works, but this is true for all manuscripts, autographs included. For instance, some of the illustrations in Fontana's Secretum de Thesauro (You are not allowed to view links. Register or Login to view.) represent devices that were already known (You are not allowed to view links. Register or Login to view., Padua, Ms. D.39). Dondi's autograph is in turn dependent on Campanus of Novara and Eastern sources and so on.