Actually doing abit of digging and the view is very spilt those who feel its a cipher of some kind have shown mathmaticly that its not gibberish. But it can be argued its possible (but would require masses of work esp. without calculaters ) to make something that would work (but there is no proof that the required knowledge existed at that point that it is belived to have been made.
What analysis was done to "prove" the manuscript is a legitimate cipher script, and how can such an analysis discern between a real cipher and carefully crafted "gibberish"?
The Voynich Manuscript is a handwritten book of about 240 pages believed to have been created in the early 15th century. It has been generally assumed to be a cipher text, but the author and purpose of the book are completely unknown. In 2009, researchers at the University of Arizona used carbon dating to confirm that the vellum pages date between 1404 and 1438. Additionally, the McCrone Research Institute in Chicago determined that the ink was "not added in a later period." This enforces the theory that the document is not an anachronistic hoax, but does not prove that the script contains a decipherable message.
A PDF presentation by Kevin Knight, Information Science Institute, University of Southern California, provides additional historical background of the document and an overview of some cryptanalysis that has been done on the document in an attempt to decipher the script. The analysis reviews patterns of individual symbols and patterns of whole words, which are inconclusive.