This is a (partial) list of proposed authors of the Voynich Manuscript.
- Roger Bacon (proposed by Wilfrid Voynich and William Romaine Newbold based on the original letter associated with the manuscript, in which it is said that Dr Raphael (ie Raphael Sobiehrd-Mnishovsky), tutor to Ferdinand III King of Bohemia, was of the opinion that Bacon was the author) - manuscript shown to be of a later date, and there is no line of connection between Bacon and the manuscript.
- John Dee and Edward Kelly - as a 'presentation piece' to Rudolph II or for some other purpose. The vellum of the document has been shown to be of earlier date. The ink has not been dated. See the McCrone Associates analysis for the Beinecke Library: (beinecke.library.yale.edu/sites/default/files/voynich_analysis.pdf) Both Dee and Kelley could have had access to older vellum. (Dee was an antiquarian and Kelley had access to the resources of Dee and other patrons in Bohemia). However they would have probably had to learn the script (and would wish to use it in other contexts).
- Jacobus Sinapius, Jan Marcus Marci and Antonio Averlino are among other possible authors who have been suggested.
- 'Outsider art' (Wikipedia page  - the vellum and other materials for creating the document were expensive, so unlikely.
- Wilfrid Voynich (and associates) as a 'document for show': a reputation to maintain, getting a sufficient quantity of 'suitable old materials' for the manuscript to look all of a piece (and why not create supporting material as well?)
- The Cathars (Wikipedia page  - no real evidence of a connection, and the dating is inappropriate.
- Someone who could write, but who was unfamiliar with the Italian script, so miscopied what they saw from an original text.
- 'Lost languages/cultures' - which have not left any other records. The question is why no other documents or traces?
- 'The prolific writer Anonymous (or one of the large Clan Anonymous)' - does not answer the question and, again, also 'why are there no other documents.'
The chief issue to be considered is - given that there would be an investment in learning the script used why it was not used in other contexts. (The 'miscopied text' might well be a one off.)
It is possible, of course, that the 'actual author(s) of the text' were not the same as the scribes(s) who put the text onto the manuscript - and there could have been a gap between original composition and actual transcription into the document we know today.